I've found lots of info on decrypting PDF files, but none on encrypting them. What tool can do this for me?
Edit: There are two good answers below, but in my specific case the PDF was a scan, not a document that I'd created.
Use pdftk. From its man page:
Encrypt a PDF using 128-Bit Strength (the Default) and Withhold All Permissions (the Default)
$ pdftk [mydoc].pdf output [mydoc.128].pdf owner_pw [foopass]
Same as Above, Except a Password is Required to Open the PDF
$ pdftk [mydoc].pdf output [mydoc.128].pdf owner_pw [foo] user_pw [baz]
Same as Above, Except Printing is Allowed (after the PDF is Open)
$ pdftk [mydoc].pdf output [mydoc.128].pdf owner_pw [foo] user_pw [baz] allow printing
pdftk has a lot of other uses as well and is worth installing if one works extensively with PDF files. To quote from the write-up in Synaptic:
If PDF is electronic paper, then pdftk is an electronic
stapler-remover, hole-punch, binder, secret-decoder-ring, and
X-Ray-glasses. Pdftk is a simple tool for doing everyday things with
PDF documents. Keep one in the top drawer of your desktop and use it
to:
- Merge PDF documents
- Split PDF pages into a new document
- Decrypt input as necessary (password required)
- Encrypt output as desired
- Fill PDF Forms with FDF Data and/or Flatten Forms
- Apply a Background Watermark
- Report PDF on metrics, including metadata and bookmarks
- Update PDF Metadata
- Attach Files to PDF Pages or the PDF Document
- Unpack PDF Attachments
- Burst a PDF document into single pages
- Uncompress and re-compress page streams
- Repair corrupted PDF (where possible)
