If any security features are turned on by the creator of a PDF document, the PDF file will be encrypted. These security features let an author disallow printing and/or copying text.

Unfortunately, the US government has (rather silly) export controls on cryptography software. This means I can't legally provide a version of xpdf that can decrypt encrypted PDF files.

Luckily, the Internet is not limited to the US (despite what certain of our government bureaucrats may believe). Thanks to Leo Smiers, Tony Nugent, and Felix von Leitner, a source patch for xpdf is available.

Instructions:

1. Download the patch file. This is a standard Unix patch file.

2. In addition to the patch file, you'll need the original xpdf source. Put the patch file (after gunzip'ing it) in the directory above the unpacked source, i.e., you should have (at least) these two things in the directory:

       xpdf-0.90/
       xpdf-0.90-fefe-diff2
   

3. Then run patch like this:

       patch -p0 <xpdf-0.90-fefe-diff2
   

   This will patch the source code in ./xpdf-0.90.

4. Recompile -- run configure and then make.