PdfConcat.net is described as 'Applet to merge or concat several sites from pdf files. No upload limits'. There are more than 50 alternatives to PdfConcat.net, not only websites but also apps for a variety of platforms, including Windows, Mac, Linux and iPhone. The best alternative is PDF-XChange Editor, which is free. Other great sites and apps similar to PdfConcat.net are PDFsam (Freemium, Open Source), PDF24 Creator (Free), Adobe Acrobat DC (Paid) and PDF Arranger (Free, Open Source).
The smallest, fastest, most feature-rich PDF editor/viewer available * Full Direct Content Editing (text based PDFs, not scanned/image based PDFs) * Includes OCR feature * View, Edit, and annotate PDF files
PDFsam Basic is a free, open source, multi-platform software designed to: * Merge PDF files (the entire documents or selected page ranges), retaining or discarding bookmarks, acroforms and generating or not a table of contents.
PDF24 Creator is free and feature-filled PDF creation, merging and conversion tool for Windows. Its unique feature among the free PDF printer tools is an editor, which allows to easily assemble, create and modify PDF files with Drag & Drop.
PDFTK Builder is a free graphical interface to for PDFtk, making it much easier to use. It is a easy to use tool to collate (merge), split, encrypt, decrypt, stamp and rotate (only 90°, 180° or 270°) pdf documents.
Nitro Pro gives you everything you need to create, convert, edit, sign, and share 100% industry-standard PDF files. It's simple, straightforward, and intuitive to use — so you can work more productively, your way.