problem running this library

[1knueller]

Hi!

Im happy you picked up that project.

I was about to merge the text comy feature myself and found your repo.

I have a problem though. You write you updated to use the newer binaries. If i try to load a document with them i get the following error:

Managed Debugging Assistant 'PInvokeStackImbalance' : 'A call to PInvoke function 'PdfiumViewer!PdfiumViewer.NativeMethods+Imports::FPDF_LoadCustomDocument' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.'

            var doc = PdfiumViewer.PdfDocument.Load(filepath);
            this.pdfViewer2.Document = doc;

[1knueller]

ok it works with the 64bit pdfium dll on 64bit project
not sure hot to get x86 to work

[ab-tools]

In case somebody else is searching, both the x64 and x86 binaries from this pdfium build seems to work fine for me:
https://github.com/bblanchon/pdfium-binaries/releases/tag/chromium%2F4194

[bachratyg]

I haven't been able to make this project work with any of bblanchon's x86 binaries. The old one (PdfiumViewer.Native.x86.v8-xfa) works but it's extremely outdated.

edit: so the problem is bblanchon's binaries are probably built without FPDFSDK_EXPORTS, and that makes the default calling convention __cdecl (see #define FPDF_CALLCONV in pdfium source). However [DllImport] defaults to __stdcall unless explicitly specified.

PdfiumViewer/PdfiumViewer/NativeMethods.Pdfium.cs

Line 664 in a7f1000

[DllImport("pdfium.dll")]

x64 is not affected because there is only one calling convention for x64.

[CanadianHusky]

Hello,
I tried 64bit winforms project and 64bit pdfium.dll downloaded from
https://github.com/bblanchon/pdfium-binaries/releases/tag/chromium%2F4194
as suggested by @ab-tools
I get
System.EntryPointNotFoundException: Unable to find an entry point named 'FPDF_AddRef' in DLL 'pdfium.dll'.
Using older pdfium.dll from Nuget PdfiumViewer.Native.x86_64.v8-xfa.2018.4.8.256 works fine.
Does anyone have any tips how to use more recent pdfium.dll ?
How did you make it work @ab-tools ? Are you able to share a minimal working example with newer DLL ?
Thank you

[CanadianHusky]

Solved. I was using pdfiumviewer.dll from original project https://github.com/pvginkel/PdfiumViewer
Once I used PdfiumViewer.dll compiled from this project, the native library mentioned above loads fine and the viewer works well.
Edit:
Even latest native pdfium.dll from https://github.com/bblanchon/pdfium-binaries/releases/tag/chromium%2F7678 Version PDFium 146.0.7678.0 (Feb 2026 works fine for 64 bit version)