i use pdftk to manipulate pdf
www.pdftk.com it is free and useable in line command
as an example
PDFTK.EXE 1.pdf 2.pdf 3.pdf cat output 123.pdf will merge 1.pdf 2.pdf 3.pdf in 123.pdf etc...
Hth
Richard
DESCRIPTION
If PDF is electronic paper, then pdftk is an electronic staple-remover,
hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a
simple tool for doing everyday things with PDF documents. Use it to:
* Merge PDF Documents
* Split PDF Pages into a New Document
* Rotate PDF Documents or Pages
* Decrypt Input as Necessary (Password Required)
* Encrypt Output as Desired
* Fill PDF Forms with X/FDF Data and/or Flatten Forms
* Generate FDF Data Stencil from PDF Forms
* Apply a Background Watermark or a Foreground Stamp
* Report PDF Metrics such as Metadata and Bookmarks
* Update PDF Metadata
* Attach Files to PDF Pages or the PDF Document
*
Unpack PDF Attachments
* Burst a PDF Document into Single Pages
* Uncompress and Re-Compress Page Streams
* Repair Corrupted PDF (Where Possible)