Does anyone have any advice or know of any tools to combine more than one pdf into a single pdf programmatically?

Here's my scenerio, I'm open to other ideas as well. In my app I have pdf attachments that are basically scanned documents that a person attaches to a certain record. There is a vfp report that gets printed that requires these attachments to be printed at the same time. I want to print the vfp report, and take each attachment, combine them into one document, and send that to the printer. I know how to send them to the printer, I would like to combine them before I do it though. Each record may have 4-5 attachments. If I want to print 20 records then all of sudden my printer que has over 100 documents waiting to print. I would like to minimize them.

Thanks!

Chris