Semi-related tip: I despise protected pdfs with a passion. Especially when you download a datasheet and you can't add annotations or highlights to it. So, how to remove this protection? One way is to print to postscript and convert back to pdf, but then you can't copy text from it.
I made a small batchfile since I never remembered that syntax,
# usage:
# decrypt.sh mypdf.pdf
# the decrypted file will be named mypdf.pdf, while the old encrypted is now mypdf.pdf-encrypted.pdf
#
echo pdf to de-secure: $1
read -n 1 -s -p "Press any key to continue"
mv "$1" "$1"-encrypted.pdf
qpdf.exe -decrypt "$1-encrypted.pdf" "$1"
echo encrypted file is now named: $1-encrypted.pdf
echo decrypted file is: $1
When I want to "protect" a PDF, I print it as a TIFF and then PDF that document. It's less "protecting" than "making it difficult to alter or copy-paste from," but it works. (Also good for ensuring your redaction blobs can't be moved.)
I always find it hard to trust free. Even with T&Cs/ToS/Privacy, if I'm not paying for it, I feel that its all lies. Combine that with a site that looks like that, and I'm assuming my PDF will have a virus attached to it.
Sure, but you're thinking about that kind of stuff even slightly, you're not going to be uploading your documents anywhere. I suspect the Venn diagram overlap between "thinks about online security" and "uploads documents to random web sites, even if they cost money" is small.
If it's anything I need to care about privacy with, I'm not uploading it to someone else's server even if I pay for it, I'm doing it locally.
But if it's say, as a friend recently experienced, a handout from a teacher in Corel Draw format, you bet your ass I'm uploading it to whatever the top google result for "convert corel draw to pdf online" is.
They are actually encrypted, but with an empty string as the (read) password.
Since this is a common 'technique' to 'protect' PDF documents, as some PDF viewers (such as Adobe reader) won't allow selecting text on these 'protected' PDF's. It's so common that most PDF tools assume an empty string if no password is explicitly supplied.
Source: I run a SaaS that converts PDF invoices to structured data, so I've examined quite a few PDF files the last couple of years.
Also, the current PDF permissions model is comically obtuse IMO. Acrobat doesn't even expose the permissions bits directly, rather each permission exposed in Adobe's UI represents various permutations of those permissions bits rather than a 1:1 mapping. It has to, because the design of that bitfield is nuts.
The semantics of the bits are described in ways that are very open to interpretation, and can be used to specify combinations of permissions that just don't make sense (example: allow content extraction for copy/paste, but don't allow content extraction for accessibility purposes, like screen readers for the blind). I suspect there are no two PDF parsers that handle that bitfield in the same way, and that it may not even be possible to implement support for it without baking in contradictions and unexpected behaviors (from a user's perspective at least). I'd be surprised if even Adobe's implementation handled it in its entirety.
If you're on a Mac, just open the PDF in Preview and then Save As to a different file name. This gives you a PDF visually identical to the original (with TOC, selectable text, etc) but with no protection.
Preview is the unsung hero of macOS. It does so much that Adobe Reader charges for: signatures, annotations, page rearrangement, plus it has the added bonus of being able to open obj and stl files.
It doesn’t do actual (cryptographic) signatures that Adobe charges for. It only does pretty pictures of handwritten signatures as an inserted object, a trivially falsifiable things.
Here's how (on windows): download qpdf (http://qpdf.sourceforge.net/) and run
I made a small batchfile since I never remembered that syntax,