PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
Documents by Readdle - A central hub for all your files.
DocuPUB - DocuPUB is an online file converter, file merger, file compressor, and file resizing tool.
Documents Pro 7 - The ultimate all-in-one mobile office suite for the iPhone and iPad with 8 premium apps in 1.
jPdf Tweak - jPDF Tweak is a Swiss Army Knife GUI application for PDF documents: combine, split, rotate, reorder...
FE File Explorer - The one-stop files solution