Try Sejda Desktop. How to Merge PDF Files. Download PDFsam Basic. While using the online tool is a free, simple solution, you might want to know how to merge PDFs using Adobe Acrobat for desktop. Online PDF combiner for Windowsand The best way to join PDF online is the Merge PDF tool of PDF Candy Drag and drop the PDF files you want to merge. The application is simple to use and has a variety of functions that make merging your documents straightforward. Below we show how to combine multiple PDF