PDF

Links

• https://www.bitsgalore.org/2021/09/06/pdf-processing-and-analysis-with-open-source-tools

Remove PDF password

• See also on Yobi
• PDF documents may have up to 2 passwords:
  • User password: protects read access to the document, and when no Owner password is specified, also protects permission settings.
  • Owner password: protects full access to the document, and protects permission settings (printing, copying...)

• Use pdftops (package xpdf) to remove password from a protected PDF. It works with either password, but when both passwords are set, it also works when only the user password is known (upon condition that permission allow Printing is set).

pdftops -upw <password> <encrypted>.pdf <decrypted>.ps              # To generate a PostScript file (e.g. for further editing)
read; pdftops -upw "$REPLY" <encrypted>.pdf <decrypted>.ps          # Same as above but don't store the password in command history
pdftops -upw <password> <encrypted>.pdf -|ps2pdf - <decrypted>.pdf  # To generate a new PDF
pdftops -opw <password> <encrypted>.pdf -|ps2pdf - <decrypted>.pdf  # When the Owner Password is known...

• An other solution is to use PDF Toolkit pdftk. However unlike pdftops this method doesn't work when only user password is known but both passwords are set.

pdftk <encrypted>.pdf input_pw <password> output <decrypted>.pdf

• pdftk can also be used to generate protected documents, and specifying permissions (eg. Printing permission).

pdftk <unprotected>.pdf output <protected>.pdf allow Printing owner_pw <ownerpwd> user_pw <userpwd>    #Allow HQ printing

• ps2pdf can also generate encrypted documents. But the generated document cannot be opened by Evince, and also it is less convenient for specifying the right permission:

ps2pdf -sOwnerPassword=STRING -sUserPassword=STRING -dPermissions=number <decrypted>.ps <reencrypted>.pdf

Concatenate PDF

Easiest is to use pdfunite from Poppler package:

pdfunite first.pdf second.pdf output.pdf

Watermark / stamp PDF

Using pdftk

# source: https://superuser.com/questions/280659/how-can-i-apply-a-watermark-on-every-page-of-a-pdf-file
pdftk in.pdf background watermark.pdf output out.pdf
pdftk in.pdf stamp      watermark.pdf output out.pdf
qpdf --overlay  watermark.pdf --repeat=1 -- in.pdf out.pdf
qpdf --underlay watermark.pdf --repeat=1 -- in.pdf out.pdf

Using PDFCreator (windows)

See Powerpoint.