Drag files into the combiner and arrange them to your liking to combine. Merge PDF Files Online for Free with the Newest Version How to combine a PDF file with a PDF file online for free on any machine with PDF viewer software Click the Select files button above and choose the option to Combine and Merge PDFs into a Single PDF. Open PDF in Acrobat Reader Click File > Open. Open a PDF file that you just want to merge in Acrobat Reader. Right-click on the PDF file, then choose Options > Merge PDF in Acrobat. Select the files you want to merge into a single document. How to Merge PDFs Online at Smallpdf.com How to combine multiple PDF files into one file with Smallpdf.com Follow these easy steps to combine PDF files into one file: Open the Smallpox app. . . . . . . Choose the option to merge a PDF with another of your PDFs.