How to combine pdf files

I have been using Adobe reader for yours but today I wanted to combine multiple pdfs into one file. Google said to go to tools then choose combine files. I was taken to a new screen that said I had to take out a monthly or annual subscription to the "reader pack" software. I selected an annual package, provided my visa card information and set up an account with a password. I then went back into tools and tried to combine my pdf files but I hit a wall. Can someone tell me what I'm supposed to do now? thank you