How to merge PDF files using Kernel for PDF Split & Merge? It is very simple. Open the Kernel for PDF Split & Merge, select 'Merge PDF' files option, enlist the PDF files, specify the page rage, and click the 'Add File' button. You can prioritize the page order as per your requirement. Finally save the merged document in a convenient location. Instead of selecting individual PDF files, you can add all the PDF files of a folder for merging.