I couldn't get the options to parse -- it kept returning me to the pod usage. I would suggest reworking this with Getopt::Long.
Also, you shouldn't 'use' both PDF::API2 and PDF::Reuse if you are giving a choice of the PDF engine, ie. I shouldn't have to install both just to use one in this script. You don't 'use' Win32::OLE -- the same can be applied to PDF::API2 and PDF::Reuse.
However, for me these are minor issues. I'm grateful just for the code to see how to call PDF::API2.
in reply to merging pdf-files: pdf-merger.pl