Hi debbief98757227,
To merge PDF files, you need to use Acrobat. If you don't have Acrobat, please feel free to give it a try! You can download a free 30-day trial from http://www.adobe.com/products/acrobat.html.
In Acrobat, choose File > Create > Combine Files into a Single PDF to merge files. (You can also use the Insert from File option in the Pages pane on the Tools panel in Acrobat to insert specific pages from one PDF into another.)
Please let us know if you have additional questions.
Best,
Sara