PDF files

edit

Open the PDF in LibreOffice, choose Tools → Redact. You can then export it within the same menu.

pdfarranger – arrange pdfs, export subsets of pages and stuff.
PDFMod – not as good as pdfarranger, use the latter ;) simple GTK GUI for shuffling PDFs around.
- Shift+Click does rectangular selections. That's a super weird design decision and disqualifies that tool for any serious usage.
pdftricks – uses GhostScript for easy manipulations.

gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/prepress -sOutputFile=output.pdf input.pdf

You can use the following parameters for -dPDFSETTINGS:

`-dPDFSETTINGS=/screen`	(screen-view-only quality, 72 dpi images)
`-dPDFSETTINGS=/ebook`	(low quality, 150 dpi images)
`-dPDFSETTINGS=/printer`	(high quality, 300 dpi images)
`-dPDFSETTINGS=/prepress`	(high quality, color preserving, 300 dpi imgs)
`-dPDFSETTINGS=/default`	(almost identical to /screen)