To combine two PDF documents using Acrobat 6.0 or 7.0:

1. With the target document open, select Insert Pages from the Document menu
2. Select Insert from the resulting menu
3. Locate and select the PDF document that you want to insert
4. Click the Select button
5. In the Insert Pages dialog box, specify where you want to insert the pages, and click the OK button

To combine two PDF documents using Acrobat 5.0:

1. With the first document open, select Insert Pages from the Document menu, or press Ctrl + Shift + I
2. Locate and select the PDF document you want to insert.
3. Click the Select button
4. Specify whether you want to insert the pages Before or After the First or Last page.  Or you can specify a specific page
5. Click the OK button