Using eDocPrinter PDF Pro Advanced Ediition og Enterprise Edition [ NOT Standard Edition ] you can merge multiple source files ( eg. Excel, Word, TXT, Image files ) into a single PDF file.
For that you will use Drag2PDF a tool which is a part of Advanced or Enterprise Edition!
Drag2PDF can do more than just merge multiple files. You can extract single pages from existing pdf files or divide an existing pdf file with many pages into multiple single pdf pages.