PDFs are great ways to pass documents around. You can even password protect them. But what happens when you come to open a PDF and it asks you politely for a password but you don't recall what the protection was. It's at times like these that you need a PDF password finder to help you find those lost strings of letters and numbers.

The degree of security on Adobe Acrobat files depends on the version of the software that was used to create the file you're desperately trying to open. Like most things to do with computers, older versions aren't as secure as newer versions.

Added to this is the person who created the file in the first place.

In fact, if you're trying to find a password this is often the first place to start.

Ebooks that you've bought are often protected by a password. Quite why, I've never worked out. After all, you've just bought the product so it's not as though you're trying to rip off the author. But each to their own.

If you're organized, you'll rename the ebook on your desktop so that the password is part of the file name. This quick and dirty method sure beats digging through past emails trying to remember what the subject of the email was so you can get to the protection.

Work based files can incorporate passwords as well. Most likely because you don't want the whole company reading your sales and profit projections. If the person who gave you the file regularly uses one particular password, start with that.

If that doesn't work, it's time to put on your thinking cap. Or splash out on a piece of software that will find the missing link for you.

Some software comes in "demo" mode first. This can be good or bad. Often the demo will only search through the first handful of possible characters and then give up unless you buy the full version.

So if you're not sure if the file will open with "london" or "new york" then this demo version may be enough to give your mind the way into the file.

But if the software is just sitting there with a smug grin on its face, with a message saying something along the lines of "Yes. I've got the password cracked. I know it and I won't tell you until you buy me" then you have a couple options:

* Pay the blackmail cost and get your file open.

* Delete the software and try the next program on your list.

* Scream to yourself and curse whoever sent you this darned password protected PDF file in the first place.

Trouble is, there are just too many possible combinations for you to be able to sit down and type them away. Even the basic 4 digit PIN that comes with your credit card has 10,000 possible combinations and that only uses numbers. If it could only use either upper or lower case letters, there are 456,976 possibilities. You've got better things to do in life than go through all those, so software is almost certainly your best solution to quickly cracking a PDF password.