narunaru;11007113 wrote:
I have searched on internet and find that it is impossible to print it directly
Don't believe everything you read.
[man]printer[/man] documentation if you're running PHP on Windows.
If you're running PHP on *NIX there are other ways. A web search for "php print pdf" yields http://www.nongnu.org/phpprintipp/ which is a class to handle IPP.
Another way would be
shell_exec("lpr filename.pdf");
which is one of the first results when searching for "php printer" (which is also how I found the Windows extension mentioned above).
But it's an FDF, not a PDF!
Well, while I've no idea what the FDF format looks like, I'm rather certain that (if it's even needed) FDFs can be saved as PDFs. I'd also suspect that an FDF is printable, with the difference from sending it to screen obviously beeing that you can't fill it out on paper and then save the updated information on the computer again. But once filled out on screen, you can most likely use lpr to print the filled out FDF. It's the first thing I'd try anyway.