Can AppendPDF Pro stamp my output documents during the appending process?

Yes. AppendPDF Pro can place stamps, watermarks, page numbers, etc. on documents. This feature is used in the Cover, TOC, and Extras blocks of the parameter file. Base 14, PostScript Type 1, True Type and Open Type fonts are supported. Margins can be modified for individual stamps as well as for full pages. JPEG, TIFF and PDF stamping is supported. See the documentation for details and instructions.