RecursiveAI.OnePdf.Fonts 1.6.0

OnePDF

A pure-managed .NET PDF library: open, repair, decrypt, extract text in reading order, read document structure, interpret pages into a drawing device or a recorded display list, and edit and save documents. Pure C# with no dependency beyond .NET itself; untrusted files are read through safe, bounds-checked code with size limits on by default.

Why OnePDF

• Opens the files that are actually out there. Cross-reference tables and streams, object streams, hybrid and incremental files, and a documented repair chain for damaged ones: trust the xref, then fix offsets and /Length by scanning, then rebuild by scanning for object headers. Every repair is recorded as a diagnostic with object number and offset (repair rules).
• Encrypted files. The standard security handler, revisions 2 to 6 (RC4 40/128, AES-128, AES-256), with user or owner password.
• Text with positions and reading order. Glyphs, words, lines and blocks; the structure tree for tagged files and geometry otherwise; right-to-left text through our own UAX #9; three plain-text modes; a versioned JSON form (layout parameters, JSON format).
• Document structure as data. Info and XMP metadata, outlines, page labels, links, annotations, embedded files, AcroForm field values, permissions.
• A content interpreter with one clean seam. page.Interpret(device) resolves everything PDF-specific (fonts, color spaces, functions, images, patterns, optional content, annotation appearances) and hands a 2D engine paths, glyph runs, finished images and shadings. PdfDisplayList records the calls and replays them, concurrently if you like (text format).
• Safe on files you did not write. No unsafe code, no pointers, no reinterpret casts. Limits (decoded size, expansion ratio, nesting, recursion, object count, operators per page, image pixels) are checked before the allocation or work they guard, and the parsers, filters and font readers are fuzzed. NativeAOT and trimming are supported.
• Editing and saving. Change objects and metadata, then write a clean new file (classic cross-reference table, or cross-reference and object streams) or an incremental update that leaves the original bytes untouched; keep, remove or set AES encryption (writing).
• Page operations. Delete, reorder, rotate, duplicate and insert pages; import pages from other documents, merge documents and split one into parts, with bookmarks, links, form fields and tagged structure carried along (page operations).
• Forms. Fill text, choice, check box and radio fields with validation, store their appearances, reset them, and flatten fields and annotations into the page (forms).
• Content creation. Draw text, paths, images and reusable forms onto new or existing pages (over or under what is there), with the 14 standard fonts or TrueType/OpenType fonts embedded as subsets with ToUnicode maps, and stamp or watermark pages (content creation).
• Signatures. Find signatures and document time-stamps, check byte ranges, digests, RSA (PKCS#1 and PSS) and ECDSA signatures, RFC 3161 time-stamps and certificate chains (to anchors you supply; nothing is fetched), and classify what changed after each signature in later revisions. Sign as an incremental update: approval or certification signatures (PAdES baseline B-B, B-T with a time-stamp from your callback, or adbe.pkcs7.detached), visible or invisible, with a local key or an external signer, and document time-stamps (signatures). Changes the specification permits after a signature are listed, not judged: see known attacks and what the result says.
• PDF/A. Write PDF/A-2b, 2u, 3b and 3u from documents made or edited with OnePDF, and from existing files that already meet the requirements: the sRGB output intent (a profile generated by OnePDF), XMP, embedded fonts, annotation flags and appearances are taken care of, and a document that cannot be written as PDF/A is refused with every violation listed, by object. PDF/A-3 files can carry attachments. It is not a validator and does not convert arbitrary files (PDF/A).
• Concurrent. Objects parse lazily into a byte-budgeted cache with single-flight parsing; any number of threads can read pages of one document at once.

Install

dotnet add package RecursiveAI.OnePdf
dotnet add package RecursiveAI.OnePdf.Fonts   # optional: substitute fonts for the standard 14

The package is RecursiveAI.OnePdf; the namespace is OnePdf (using OnePdf;). Target framework net10.0. Moving from PdfPig? See the migration guide. Moving from PDFsharp? See that guide.

Quick start

Open a document, look at pages and metadata. PdfDocument is IDisposable: it holds the file open and reads it by position, so dispose it (a finalizer covers forgetting, but don't rely on it). Page indexes are zero-based.

using OnePdf;

using PdfDocument doc = PdfDocument.Open("in.pdf");
Console.WriteLine($"{doc.PageCount} pages, PDF {doc.Version}");

PdfPage page = doc.Pages[0];
Console.WriteLine($"{page.CropBox.Width} x {page.CropBox.Height} pt, rotated {page.Rotate}, label {page.Label}");

DocumentInfo info = doc.Info;                       // the Info dictionary
Console.WriteLine($"{info.Title} / {info.Author} / {info.CreationDate}");
Console.WriteLine(doc.Xmp?.Title);                  // XMP, when present

// No exception for a file that will not open:
if (PdfDocument.TryOpen("maybe.pdf", out PdfDocument? other, out PdfException? error))
    other.Dispose();
else
    Console.WriteLine(error?.Message);

Sources can be a path, a seekable Stream (left open with LeaveOpen), a non-seekable stream (copied; use OpenAsync), or a ReadOnlyMemory<byte>. If the file changes underneath an open document, reads throw PdfSourceChangedException.

Text

using OnePdf;
using OnePdf.Text;

using PdfDocument doc = PdfDocument.Open("in.pdf");

// Every page, in parallel (min(4, cores) by default), headers and footers flagged by their repetition.
IReadOnlyList<PdfPageText> pages = doc.ExtractText(new PdfTextOptions { Mode = PdfTextMode.ReadingOrder });
Console.WriteLine(pages[0].Text);                              // plain text, in the chosen mode

// One page, by itself.
PdfPageText text = doc.Pages[0].ExtractText();

foreach (PdfTextWord w in text.Words)                          // words with positions (PDF points, y up)
    Console.WriteLine($"{w.Text} {w.Bounds}");

foreach (PdfTextBlock block in text.Blocks)                    // blocks > lines > words, in reading order
    foreach (PdfTextLine line in block.Lines)
        Console.WriteLine(line.Text);

Plain-text modes are ReadingOrder (default), ContentOrder and Layout (spatial, like pdftotext -layout). Ligatures are decomposed, presentation forms (Kangxi radicals, Arabic and Hebrew forms) are folded to their base characters, /ActualText replaces its span, and invisible text (such as an OCR layer) is included and flagged IsVisible = false. The Unicode chain is ToUnicode, then glyph names through the Adobe Glyph List, then the font's own cmap, then predefined CMaps, then U+FFFD. OnePDF does no OCR.

Whole-document doc.ExtractText() does not keep each page's glyph list, so a long document stays small; words, lines, blocks and every plain-text mode are still there, and pageText.ReadGlyphs() reads a page's glyphs on request. Single-page page.ExtractText() keeps them. Set PdfTextOptions.RetainGlyphs to choose either way.

Interpret a page

using OnePdf;

using PdfDocument doc = PdfDocument.Open("in.pdf");

var list = new PdfDisplayList();            // an IPdfDevice that records
doc.Pages[0].Interpret(list);               // or pass your own IPdfDevice

Console.WriteLine($"{list.ItemCount} items");
File.WriteAllText("page1.txt", list.ToText());   // the versioned text form
list.Replay(new PdfDisplayList());          // replay into any device; safe from several threads

The device receives paths in user space with the full matrix, final colors, glyph runs with identity and Unicode, finished image buffers with masks, and bracketed groups and soft masks. JPEG, JPEG 2000 and JBIG2 data are decoded through an IPdfImageDecoder registry you fill; with none registered, the device gets the encoded bytes and a diagnostic.

Passwords

using OnePdf;

try
{
    using PdfDocument doc = PdfDocument.Open("secret.pdf", new PdfOpenOptions { Password = "hunter2" });
    Console.WriteLine($"{doc.Encryption?.Cipher}, {doc.AccessLevel}, {doc.Permissions}");
}
catch (PdfPasswordException)
{
    Console.WriteLine("wrong or missing password");
}

Either the user or the owner password opens the file. doc.Permissions exposes the permission flags; OnePDF does not enforce them, and honouring them is the application's job.

Limits, diagnostics and errors

using OnePdf;

var options = new PdfOpenOptions
{
    Strict = false,                                         // default: repair and record instead of throwing
    Limits = PdfLimits.Default with { MaxDecodedStreamBytes = 64L << 20, MaxObjects = 1_000_000 },
};

try
{
    using PdfDocument doc = PdfDocument.Open("untrusted.pdf", options);
    doc.Pages[0].Interpret(new PdfDisplayList(), cancellationToken: CancellationToken.None);
    foreach (PdfDiagnostic d in doc.Diagnostics)            // what was repaired or skipped
        Console.WriteLine(d);                               // severity, object number, offset, message
}
catch (PdfLimitException e) { Console.WriteLine(e.Message); }
catch (PdfFormatException e) { Console.WriteLine(e.Message); }

• Lenient by default. Unambiguous repairs and skipped operators become PdfDiagnostics on doc.Diagnostics. A page that cannot be parsed throws only when you access it. PdfOpenOptions.Strict turns warnings into errors.
• Exceptions are PdfFormatException, PdfPasswordException, PdfEncryptionException, PdfLimitException and PdfSourceChangedException (all PdfException), plus argument exceptions, OperationCanceledException and I/O exceptions passed through.
• Limits are on by default (PdfLimits.Default: for example 256 MiB per decoded stream, an expansion ratio of 1100 after the first 16 MiB, nesting 256, 2^23 objects, 2^24 operators per page, 2^28 image pixels). PdfLimits.Unrestricted turns them off. Wall-clock limits are yours: pass a CancellationToken.

Redaction

doc.Redact(regions, options) removes the glyphs, paths, image samples, annotations and form values under given areas by rewriting the content, so extraction and a byte search of the saved file find nothing of them. Pages it cannot read completely fail the call and leave the document unchanged. What is and is not covered is in redaction.

using PdfDocument doc = PdfDocument.Open("in.pdf", new PdfOpenOptions { AllowEditing = true });
doc.Redact([new PdfRedactionRegion(0, new PdfRectangle(72, 600, 300, 620))], new PdfRedactionOptions { Overlay = new PdfRedactionOverlay() });
doc.Save("out.pdf");

Security

OnePDF never runs code or touches the network. JavaScript, actions and URIs in a document are data that you can read, never executed or fetched. External stream references are treated as empty with a diagnostic. XFA is raw XML and is never rendered. Embedded files are read only when you ask. The only files OnePDF opens are the document you give it and, through the font provider, local system fonts. The code is safe C# with no unsafe, Unsafe.* or MemoryMarshal.

What it does not do

• No PDF/A validator or converter (existing files are checked and refused, never rewritten into conformance), and no long-term validation data (/DSS, PAdES B-LT/B-LTA) when signing. Field scripts are never run, so calculated fields are not recomputed. New text is laid out without a shaping engine, so complex scripts (Arabic, Indic and similar) are not shaped.
• It does not render pixels. OnePDF resolves a page into drawing calls; a 2D engine paints them. Rasterizing is planned as a separate package, RecursiveAI.OneImage.Pdf, built on OneImage; it is not available yet. It will implement OnePDF's device and register PDF as an image format. OnePDF has no imaging dependency.
• No OCR. Scanned pages without a text layer give no text.
• Missing annotation appearances are generated for form fields and simple markup only (see appearance generation); other annotation types without one draw nothing and record a diagnostic.
• Public-key encryption is not supported yet. Encrypted files need the standard handler and the BCL's AES, which browser WebAssembly lacks (those files fail with a typed error there).
• Permissions are reported, not enforced.

Packages

Register the substitutes once at startup; documents that do not embed Helvetica, Times, Courier, Symbol or ZapfDingbats (or their Arial, Times New Roman and Courier New aliases) then get outlines from the package, behind any matching installed font:

OnePdf.Fonts.FontsPackage.Register();   // before opening documents; calling it again is harmless

The Fonts package ships the upstream font files unmodified under the SIL Open Font License 1.1, so its license expression is (MIT OR Apache-2.0) AND OFL-1.1: the code is MIT OR Apache-2.0, the fonts are OFL. Each font's license text and copyright lines are in the package under licenses/. The fonts are never offered on their own. Core stays MIT OR Apache-2.0; the data tables it embeds from Adobe and Unicode, with their notices, are listed in THIRD-PARTY-NOTICES.md.

Platforms

Target framework net10.0 on any platform .NET 10 supports. CI builds, tests and publishes a NativeAOT smoke app on win-x64, linux-x64, linux-arm64 and osx-arm64. The library has no reflection, dynamic or runtime code generation, so it is trim- and AOT-compatible (IsAotCompatible and IsTrimmable), with warnings as errors. Output is deterministic: the same input gives the same geometry and the same text on every platform.

Benchmarks

OnePDF against PdfPig 0.1.16 on the same files, in the same process, for each task: wall-clock time and peak memory, each at degree of parallelism 1 and at the default degree (min(4, cores), so 4 here). Parallel figures are shown on their own rows and are never single-thread results. PdfPig has no parallel mode; at the default degree each worker opens its own copy of the file and extracts a run of pages. Open and metadata work is single-threaded in both libraries. Speedup is PdfPig time divided by OnePDF time.

OnePDF is faster on every row. The smallest margins are single-thread born-digital text (1.13×) and metadata of a small file (1.10×, about 2 µs). Allocation is lower throughout: for example 62 MB against 562 MB for the 300-page text row at degree 1.

Information rows (not part of the comparison above):

Whole-document extraction drops each page's glyph list by default to keep long documents small; keeping them costs time and about 2.3× the peak memory on the 300-page file (single-page extraction keeps them).

PDFium and mutool use less peak memory than OnePDF. On born-digital text, PDFium peaks at 43 MiB and mutool at 45 MiB against OnePDF's 104 MiB at degree 1 (112 MiB at the default degree); on the scan and CJK files the gap is smaller (PDFium 52 and 42 MiB, mutool 43 and 44 MiB, OnePDF 56 and 66 MiB). The PDFium figures go through Docnet.Core at one thread; the mutool figures include starting its process, and its peak includes the child process.

Method. Measured on a dedicated workstation (AMD Ryzen 9 7950X3D, 16 cores / 32 threads, Linux Mint 22.3 x64, .NET SDK 10.0.402, runtime .NET 10.0.13); other jobs were held off during the run. Times are BenchmarkDotNet 0.15.8 means with the default job and [MemoryDiagnoser]. Peak memory is the process's maximum resident set (/usr/bin/time -v), one cold process per row, and includes the .NET runtime itself, so the differences matter more than the absolute figures. Load average (1 minute) was 1.18 at the start, 1.40 when BenchmarkDotNet finished and 1.53 at the end, and stayed between 1.06 and 2.83 in the 30-second trace during the run. Inputs and the benchmark project are in bench/; the files are generated by tools/corpus/make_bench_inputs.py. The mutool rows come from a second run on the same machine and commit (load 1.25 at the start, at most 1.31). Results are for these files on this machine; yours will differ.

Text extraction quality

Character error rate on content (order-free) and reading-order error, in percent, lower is better. PdfPig is shown as its default Page.Text and as its documented layout pipeline (Docstrum blocks plus unsupervised reading order); on the real-world set the PdfPig figure is the better of the two for each metric and category, best of 8 runs.

How it is measured, and the per-category tables: tools/OnePdf.Quality and testdata/realworld. Reference text is the PDF's text layer in logical order, so an extractor that emits right-to-left text in visual order scores worse by design.

Robustness

Over the test data and three public corpora, GovDocs1 (5,767 files), a 5,000-file sample of SafeDocs CC-MAIN-2021-31 and the veraPDF corpus (2,906 files; fetched by script, not committed), PdfPig opened no file that OnePDF failed to open, and OnePDF opened 20 files PdfPig did not. A sweep that opens each file, extracts all text and interprets every page, with default options, found 0 crashes and 0 hangs (slowest page 0.40 s, highest peak memory 889 MiB). The 13 fuzz targets (parser, document and repair, typed model, interpreter, filters, CCITT, decryption, PDF fonts, font programs, CMaps, shadings, Type 4 functions and text extraction) each ran 600 s under libFuzzer with no findings.

Building

dotnet build
dotnet test
dotnet publish tests/OnePdf.AotSmoke -c Release -r linux-x64 -warnaserror

Build output goes outside the source tree. Set ONEPDF_ARTIFACTS to choose where; without it, output goes to artifacts/ at the repository root, which is ignored by git.

License

Licensed under either of MIT or Apache-2.0 at your option.

Copyright (c) Recursive AI, LLC. Third-party data and fonts are listed in THIRD-PARTY-NOTICES.md.