How Do I Merge PDF Files With Adobe?
In Adobe Acrobat 9 Pro, merging or combining PDF files is a fairly simple task. Open Adobe Acrobat, and select File – Combine – Merge Files into a Single PDF… (Figure 1) or Combine – Merge Files into a Single PDF… from the Tasks toolbar.

Figure 1
This will bring up the Combine Files dialog window (Figure 2). This dialog allows you to browse to and select the desired files, change the order of the files in the new PDF, and even select the target file size (Smaller, Default, Larger) of the resulting PDF.
Figure 2
Click on the Combine Files button, and Acrobat does the rest. The resulting file will then open in Acrobat for saving and/or any additional modification.