There are several ways to combine multiple PDFs into a single file on a PC/Windows:
(1) Using desktop software like Adobe Acrobat (note: Adobe Acrobat is the paid-for version, not the free Adobe Reader). You can download and use Adobe Acrobat on a trial basis (click the link above, then click the Free 30-Day trial button on the right).
(2) Using free dedicated tools like PDFsam ("PDF Split and Merge”). This tool allows you split and merge PDF files. It is completely free and open-source. Once installed, open PDFsam, select Merge/Extract on the left menu, Add your files, select an output destination, and press Run.
(4) Printing a paper copy of all materials and then using your copier's "Scan to PDF" function to produce a complete PDF. This method is recommended only as a last resort as it results in a much larger file size.