Combining PDFs can be a pain in the butt. Adobe only lets you do it in Adobe Acrobat Standard or Pro (here’s a how-to on that) and other software I’ve used costs money, requires installation, or limits the number of pages you can combine. I ran across this site today which let’s you combine as many PDFs as you need without a mandatory cost. I suggest you donate though as this is a lifesaver. Bookmarked!