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 To Ppt Converter 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
OR A native Windows application. The main screen looks like this when you run it from its command window. (The left view is that of PDF viewer software; the right is thumbnails view.) On thumbnails view, clicking the three dots button at the bottom (and selecting PNG or JPG’) opens the PDF image in a native Windows image viewer that displays its source image. (That picture is the PDF page's title bar.) On the next display (and clicking load image’), you load the desired image into the viewer on a page whose title bar is visible. This process can be repeated with an image in several formats. Note that if you select image format JPEG’ you can choose to have a specific page of the file converted. PDF To PPT Converter works in Windows 10 and 10.1—and, as usual, it is free. PDF to Word This Windows application also works with PDF files that are.