PdfDocument::Flatten() improperly named; doesn't flatten form fields

[LittleBoxOfSunshine]

Reporting an Issue Here

https://github.com/empira/PDFsharp/blob/5aa7afeb13270aaca36ad21edcf3cc62d6c5446c/src/PdfSharp/Pdf/PdfDocument.cs#L854-L863

Form flattening has a specific meaning in PDFs where the form fields will be removed as a result of the process. In many circumstances, flattening is just used to disable editing but it has other side effects such as changing the document structure and reducing file size that specific use cases are dependent on. Form flattening is non-trivial to implement, and while this workaround accomplishes the desired effect in some use cases it introduces confusing bugs when the user is performing actions dependent on the form being truly "flattened". In my opinion this function is useful but should be given a different name such as MakeReadOnly, ReadOnly, DisableEditing, etc. that doesn't conflict with the common meaning of flatten.

Expected Behavior

The form fields will be removed and replaced with their contents as regular markup objects

Actual Behavior

The form fields are set to read only mode.

This is a great project that has been extremely useful for me, and I'm definitely nitpicking here but I think it's worth considering so that other consumers of the library don't end up down the same confusing debugging road I did. Thanks for the great work!

[MoishyS]

Would be great if you can add real flattening (basically all "print to PDF" are doing it)
http://forum.pdfsharp.com/viewtopic.php?f=3&t=3783&view=next#p11641

[derekdevv]

I tried forked version :
https://github.com/packdat/PDFsharp/tree/AcroForms

and its flatten method is flattening my text fields properly (except there's a slight alignment issue).
Hope this info will help future implementation of the flatten method.