You need a svg file called stamp.svg which is the template to stamp the files. It can contain anything you want but also a line of text with some content such as, e.g., xxx-poster.pdf, which will be replaced by the name of the file itself (the stamp). This must be fixed by hand in the source:
$line =~ s/xxx-poster.pdf/$file/;
Also the filter of which files to stamp should be set manually in the source, e.g.:
@files = <*-poster.pdf>;
Create a directory stamped, the destination for the stamped files.