It's easier to see errors if you put a use strict; and use warnings; at the top of your code.

Where did you get the Acrobat::FDF module? It's not on CPAN.

You should note that the order that data comes out of the database is not guarenteed unless you explicitly tell it otherwise. This means you should avoid using SELECT * (except for interactive use) and instead explicitly write the columns you want, such as SELECT id, ammount, copy, [REST_OF_COLUMNS] [REST_OF_STATEMENT].

Instead of printing the content type yourself, have CGI.pm generate it: print $data->header( content_type => 'application/vnd.fdf' );.

Is this really your first non-trivial Perl code? It's one of the cleanest newbie programs I've seen.