Just an off the hip idea, but are you absolutely certain that the modules (particularly Acrobat::FDF) exist on your server? If not, then any of them spitting out an error message of any sort would cause the error you see of premature end of script headers.

If they do exist, then perhaps there's some other error in your script, that print's out an error message of some sort or another, thereby causing the error you see. You may wish to move your header printing to as soon a point as possible in your script, maybe even in a BEGIN block, (but you'd have to ask other monks for assistance on that, as I'm a little fuzzy on the specifics.)

Good luck.