Tideway.PdfTools

In-memory PDF merge and password encryption for .NET, backed by the native qpdf library. No temp files — byte[] in, byte[] out.

using Tideway.PdfTools;

byte[] merged     = PdfTools.Merge(pdfA, pdfB);              // pages of B appended to A
byte[] combined   = PdfTools.Merge(new[] { a, b, c });       // n-way merge, in order
byte[] locked     = PdfTools.Encrypt(pdf, "password");       // AES-256 (R6) password protection
byte[] unlocked   = PdfTools.Decrypt(locked, "password");    // remove password protection
bool   locked3    = PdfTools.IsEncrypted(pdf);               // incl. password-protected files
byte[] fastWeb    = PdfTools.Linearize(pdf);                 // "fast web view" for browser streaming
byte[] chapter    = PdfTools.ExtractPages(pdf, 3, 7);        // pages 3-7 (1-based, inclusive)
List<byte[]> each = PdfTools.SplitPages(pdf);                // one single-page PDF per page
int pages         = PdfTools.PageCount(pdf);

Failures (corrupt input, password-protected input) throw QpdfException carrying qpdf's full error text. qpdf warnings on slightly malformed PDFs are tolerated.

The raw qpdf C API surface is exposed as Qpdf for operations the wrapper doesn't cover.

Native library

This package P/Invokes libqpdf, resolved in this order:

1. QPDF_LIBRARY_PATH environment variable — full path to the shared library; overrides everything.
2. NuGet runtime assets — runtimes/{rid}/native/ binaries bundled in the package, when present.
3. System-installed qpdf — probed under the usual per-platform names, including versioned sonames (libqpdf.so.28–30, libqpdf.28-30.dylib, qpdf28-30.dll) and Homebrew/MacPorts locations (/opt/homebrew/lib, /usr/local/lib, /opt/local/lib).

Installing qpdf per platform:

Platform	Install
macOS	brew install qpdf
Debian/Ubuntu (incl. containers)	apt-get install libqpdf-dev (the runtime package alone ships only versioned sonames, which the resolver also finds)
Windows	qpdf release zip from https://github.com/qpdf/qpdf/releases — put qpdf*.dll (and its companion DLLs) next to the app or on PATH

Bundling native binaries in the package

To make the package self-contained, drop platform builds into runtimes/ before packing:

runtimes/win-x64/native/qpdf.dll
runtimes/linux-x64/native/libqpdf.so
runtimes/linux-arm64/native/libqpdf.so
runtimes/osx-x64/native/libqpdf.dylib
runtimes/osx-arm64/native/libqpdf.dylib

The .NET host then loads the right one automatically per platform/architecture. Note that libqpdf dynamically links libjpeg and zlib on most distro builds — bundled binaries should be built with static dependencies (or shipped with their companion libraries) to load reliably everywhere.

CI-built native binaries

The Build qpdf Natives workflow (.github/workflows/build-qpdf-natives.yml) produces exactly these binaries: qpdf built from source for all five RIDs with zlib and libjpeg-turbo statically linked in and qpdf's own native crypto provider (no OpenSSL/GnuTLS), verified per platform to have no dynamic dependencies beyond OS defaults, plus qpdf's Apache-2.0 license alongside.

1. Run the workflow manually (GitHub → Actions → Build qpdf Natives → Run workflow); optionally override the qpdf release tag (default v12.3.2).
2. Download the combined qpdf-runtimes artifact from the run.
3. Extract it into runtimes/ so the files land at runtimes/{rid}/native/….
4. dotnet pack PDFTools.csproj -c Release.

The run also uploads a tideway-pdftools-nupkg artifact — the package already packed with the binaries in place — if you'd rather skip steps 3–4. Nothing is pushed to a feed and no binaries are committed to git.