There are Three basic ways you might want to use the Merge feature: either merge pages or merge entire PDF files.
1. Click Tools on the main menu -> Editor -> Merge;
2. Add Files you want to combine;
3. Set the page range and page size as you desire.
1. On the main menu, click File -> Merge PDF Files;
2. Select the PDF file(s) you want to add to the existing one and press Open;
1. Select Editor on the toolbar -> Merge -> Add Files;
2. Add one or more PDF files to merge in batch.
3. Set the page range and page size as you desired.