Many PDF Editor support this. I recommend getting a application to do this because it tends to have features that you may need after you combine the multiple PDF into one. For example, you may need to delete some pages, organizing the pages, or adding a new page for a table of content.
Steps for Multipage PDF 1) Go to File, Open, Open with…2) Select PDF Split 3) Choose Page Split as PDF Split 4) Click Ok Steps for single PDF 1) Open the PDF, you will see a screen that ask to convert page to PDF.2) On the Convert page window, Select all pages in PDF, in this order:Page1Page2Page34, as per requirement.