encryption doesn't work on some pdf files

[terceiro]

a simple pdf encryption doesn't work on origami 2.1.0, e.g.:

pdfencrypt --output /tmp/enc.pdf --password test plain.pdf

then opening the resulting pdf with a pdf viewer, I cannot decrypt by using "test" as password. the sample pdf is attached, and was produced with a simple echo hello | pandoc -o plain.pdf. However, I tried with a PDF file generated from LibreOffice, and it worked.

This did work in 2.0.0. I bisected this locally, and found the commit that breaks this is dde7ab1.