I have project in .net framework 3.5 to merge files (pdf,doc,docx,xls,xlsx) to one single pdf file (or another type above in single files). Additionally, it can add header, footer, page number. Can you make recommendation the library that appropriate to this requirement? Notes: I've already tried pdfsharp. It can manage to merge files, add footer, header and page number, but it can't modify another file except .pdf files.