I have a .pag file and I need to know what is the data it is storing, what is the the format of data.

According to Google this file extension is associated with at least six different programs/formats. Since we can't see your file, you'll have to do some investigating yourself. Do you have any idea who generated this file (ask them!), and with what software? If you really don't know, and you happen to be on a *NIX system, try these two commands: file FILENAME and hexdump -C FILENAME | head to get some hints as to what it might be.