One of the key features of PDF format is the security. There are two kinds of PDF password. Setting the ”’user”’ password will prevent anyone from opening the PDF file without it. Using the ”’owner”’ password, you can restrict others from copying, modifying, or printing the document.

However, PDF security can also be a problem. If you or your company lose the ”’user”’ password for your own files, you may have a serious problem.

Alternately, you could be legally entitled to mark-up, make notes on, and extract portions of someone else’s document, but if they have set the ”’owner”’ password (to prevent you from distributing a modified version of their document), you may not be able to make those changes, even for your own use.

”’WARNING”’

In these cases, you may be able to work around the PDF security restrictions, but be careful. Depending on the country in which you reside, attempting to crack any encryption software could be highly illegal, even if you own the content. Make sure you are legally entitled to access the data before attempting any of these methods, and do not break any applicable laws.

”’When you cannot copy or modify the PDF file, try a non-Adobe ”Print to PDF””’

Researchers reviewing papers often like to highlight important phrases, but if the file you’ve downloaded from your library is locked, you may not be able to mark-up the electronic copy.

Try printing the document to PDF again, but using a non-Adobe PDF converter. It should look the same, and you will be able to modify the new version, so you need not print it out before reading it.

”’When you cannot copy or print the PDF file, try Gmail”’

To extract the text from a protected PDF file, try mailing it to your Gmail account, then using the "View as HTML" option. This should allow you to copy the text and (most of) the images, and to print a version of the file, though the layout may not be correct. If the files are too large, this may not work.

”’When you cannot copy or print the PDF file, try a Password Remover”’

You can often remove the ”’owner”’ password using [http://www.anypdftools.com/pdf-password-remover.html#163 AnyBizSoft PDF Password Remover] or [http://download.cnet.com/1770-20_4-0.html?query=pdf+password&searchtype=downloads similar software].

”’When you can not open the PDF files, try Password Recovery”’

Cracking the ”’user”’ password is very difficult and time consuming. There is password recovery software that typically will use a [http://en.wikipedia.org/wiki/Brute_force_attack brute force] approach, trying all possible combinations. These methods of cracking could take days or even longer, but should produce results eventually.