[AnotherCat]

I use either PDFCreator or Primo PDF (and there are others too, but those are just the two I have used for many years). Sometimes one will work better than the other.

They will convert some other file types to PDF and also join PDFs together into one and do all the postscript stuff automatically; they install as printers. So whatever one wants to be converted to PDF (assuming supported) one just opens that file (so if a PDF, open in whatever it is that you use for reading those) and print it, select PDFCreator or Primo PDF as the printer and print and it will create the PDF file with the name you select.

To join multiple files (they do not have to be all of the same type) into one book with PDFCreator is pretty obvious, but in PrimoPDF not so; print the first file of the new book and when asked give it a file name, then print the second file and give it the same name as the first which then asks whether to Append or Overwrite, so one just appends; keep repeating in the correct order as they are to be in the final book for however many files one has.

For inserting or removing pages I use PDF Split and Merge (that thanks to Jackie_W's lead). As the name infers, it also merges files too.