You could try this
A program called AEBPR (Advanced eBook Processor) may help. If you google AEBPR you will find it.
I don't know whether it will handle that kind of encryption (I suspect not) but many PDFs it does handle - I use it for similar purposes myself if I want to annotate or edit PDFs.
It's a Windows program, but it works perfectly under WINE and/or Crossover on OS X 10.5 in my experience. Once WINE or Crossover is installed, you simply run the installer, then run the application, which will launch in a demo mode. Then close it, and run Regedit (which WINE includes a version of) and follow the instructions in the archive on how to add the registration key to the registry. Running the program will have added the appropriate key, you just need to put the registration code in a STRING value. It's all in the instructions and takes a minute or so - much easier than it sounds.
Hopefully I'm OK posting this (if not, please remove it - nothing inappropriate intended). It is essentially abandonware - it was released into the wild to get round an Adobe lawsuit against the programmer and also in the hope of getting donations for his defence, Dmitry Skylarov that was big news a few years back. Adobe lost, but the software is no longer for sale and is all over the place on the net quite openly - it's just 'fair use' stuff.
Other than that, something like GuaPDF which is more modern and actually does password cracking rather than simply going round the pathetic security that PDF used to use, so should work on some newer encryption, but takes time. There are probably endless other options out there - google PDF Decryption Mac or something.
The other thing you could do, is if the encryption settings allow for printing, you could just print them to a PDF creation program on a computer. I'm not sure what combination of viewer and creation you would need though - acrobat and acrobat reader won't do what you need, on Mac anyway, as far as I know. Preview.app might.
There's another PDF annotation program called PDFXChange Viewer - again it's a windows program, but it has a portable version which is free and works with WINE and Crossover nicely. It may be more flexible in terms of what it will allow you to print, but I have no way to test it right now. Failing that, some linux viewers may ignore restrictions. Like someone said, Preview used to, but I don't *think* it does any more. I don't have a mac any more to test on, having given up on my macbook air after some hideous service from an Apple Store.
Final possibility (only does one page at a time, but you can specify the page) - Inkscape is a free graphics program capable of editing PDFs. I have NO idea what happens with encrypted ones though, and it will depend not only on the encryption used but also the actual permissions they've set.
