How to Scan Multiple Pages into one PDF File?

Open Adobe Acrobat Professional, from the File menu, scroll down to Create PDF > From Scanner… as follows:
Then you will get a dialogue:

Then press the Scan button.

After scanning the first page, you will be presented with another dialogue to print the second page. Now you should place the front of page 2 in the scanner, this is the way that the software will know its part of the same document (or set).