[Podofo-users] Modifying encrypted PDFs changes encryption settings?

[<joh...@gm...>]

Hi,

I'm using PoDoFo in an iOS project to open and modify encrypted (and
non-encrypted) PDFs.  I'm using PdfMemDocument::Load(), catching the
exception when a password is required and then calling
PdfMemDocument::SetPassword().  I then use a PdfPainter to make some
modifications before I write everything out at the end with
PdfMemDocument::Write().  This all works fine except that I'm seeing
an issue on OS X with Preview.app and on iOS with the built in PDF
viewer.  The issue is that while Acrobat, and Google Docs (the only
other readers I've tried), require me to enter a password to view the
modified file, Preview and the iOS reader do not.  To them, the
document appears to be completely unencrypted.  I was hoping that
making modifications to an encrypted PDF would preserve the original
encryption settings, but that doesn't seem to be the case (the
original document was encrypted with Preview and appears encrypted to
Preview).  Am I doing something wrong?  Is this possibly an issue with
Apple's software?  I can post code if necessary.  Thanks.

- John