Today, when I clicked on one of my numerous infected PDF files using someone else's windows computer, I was surprised Notepad opened it instead of Adobe Reader.
I use live Linux DVDs on my laptops. Booting to live PCLinuxOS FullMonty offline, I opened the PDF file with Kate. Kate displayed numerous wierd characters: dominoes with characters inside, characters with dots on top of them, asian characters and numerous white rectangles indicating white spaces. Kwrite used to warn about white spaces.
A search for malicious white spaces brought up SLQ injection and PHP injection. My linux boxes are being hacked so I used a windows computer to copy and paste the contents of the Kate file into pastebin. Notepad could not display the white spaces. http://pastebin.com/9LUCUbFV
This PDF file is graphical. Evince Document Viewer did not offer the option to click on edit > select all > copy and then paste into a plain text file.
Two years ago, KlamAV and ExeFilter detected numerous unreadable PDF files. I converted my text based PDF files into plain text files. Evince Document Viewer offered option for text based PDF files to select all, copy and paste into plain text files. Then I deleted all the texted based PDF files.
I searched for a graphical format that was not prone to malicious code to convert my graphical PDF files. I could not find one. I don't know how to quarantine my graphical PDF files.