On a Apple computer, the “Print” function of the “Preview” app includes the choice for printing the open file to PDF. This works for converting various picture formats to PDF. In fact, any open printable file can be printed as a PDF. If your objective is to make a PDF into a searchable PDF, Pdf Merging Online works. There are some “free” software listings on the Internet, but I can’t suggest one or another. On a Apple computer, if you just want to merge two or more PDF files, click theft-most icon above the main PDF window. There’s dropdown with several choices. The second is to open “thumbnails”. Click it; you get thumbnails of every slide in your PDF file. Do this with both of the files you want to merge. Drag thumbnails from one file to the other - in the order you choose. You now have the merged file. (This is probably identical in the Windows operating system.) HTH
O, THE “NEW’ PDF EDITOR! The best of everything — no matter what your need. It’s so easy to use. Do I need ’two’? click the arrow to the right to view a separate page of the PDF viewer. ‖ And do you know how to? ‖ (For Windows or OS X, ) if you just want to merge two or more PDF files, click the theft-most icon above the main PDF window. Click it; you get thumbnails of every slide in your PDF file. Do this with both of the files you want to merge. Drag thumbnails from one file to the other — in the order you choose. You now have the merged file.