PDF Merge for Free
Please just let us merge PDFs, that is not worth 20$/month if that is all we do with it, once in a while! (I don't own a mac and cant use preview)

-
VIVEK CHOUDHARY commented
Need to find the simplest method to join multiple PDFs in single PDF? Download CubexSoft PDF Merge Tool on system. It works on all Windows OS i.e. 7, 10, 11, Vista, etc. and Mac OS editions like High Sierra, EI Capitan, Yosemite, High Sierra and many more. Users can simply load the PDF file by using dual options i.e. Add File(s) or Add Folder as per user’s need. It allows users to save the resultant output in the preferred destination area. During the process, users can easily merge the PDF files with the help of its merge options i.e. split merged by file size, merge pdf by page range and many more. Also download its demo version that permits to merge first 5 PDF files/folder free of cost.
Know More: https://www.cubexsoft.com/pdf-merge/