How can I scan multiple pages into a single PDF?

"As of OS X 10.8, Preview can also do it. Follow these steps:

Select ""File"" > ""Import from Scanner"".
A dialog will open, with an overview of the document to be scanned.
In that dialog, in the ""Format"" menu, select ""PDF"". If you do not see this dropdown, it's because you have to click on the ""show details"" button.
Below will then appear the checkbox ""Combine into single document"". Check it.

Note: do NOT miss the 3rd step. If you don't select ""PDF"" as the format, the ""Combine into single document"" checkbox will NOT appear."

Have you considered an Automator workflow? It comes with a "Combine PDF pages" action, as well as renaming ones.

OfficeDrop is good for this. I've been using it for a while on Windows, and it works nicely. Unfortunately, while the Windows version is free the Mac version costs $20.

"Purchase Adobe Acrobat Pro.

Select Create PDF.

Select From Scanner.

Hit Scan.

When the prompt appears, select Scan Page 2 after putting page 2 into the scanner.

Repeat for the rest of the pages in that document, repeat entire instructions for the next document."