What are some alternatives?
When comparing PDFMerge and Adobe Acrobat DC, you can also consider the following products
PDFsam - PDFsam Basic, a free, open source, multi-platform software designed to split, merge, extract pages, mix and rotate PDF files
PDFelement - All-in-one PDF editor
PDFMate Free PDF Merger - PDFMate Free PDF Merger works as a PDF Joiner, PDF combiner, PDF breaker, image to PDF converter and PDF encryptor. With PDF Merger, you can batch merging pdf files, combining specified pages or converting scanned image file to create new PDF file.
Google Drive - Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
PDFill - Open, View, Edit, Save and Print PDF Documents without Adobe Acrobat
Foxit PhantomPDF - Edit PDF files with our feature-rich PDF Editor. Download Foxit PDF Editor to convert, sign, scan / OCR & more. A speedy PDF Editor alternative to Adobe Acrobat.