PDF Image Stamp is a high performance server tool from Traction Software for Windows PC, Unix Aix, Linux & Macintosh OSX
NOTE: This Software does NOT require Acrobat, PDF Image Stamp is designed for server usage.
PDF Image Stamp Server software automates the process of applying JPEG Images to different sized pdf's
PDF Image stamp contains many special features like starting from any page, 1 in nth pages, x,y positioning on the page, image size scaling, image opacity, flip horizontal page, flip vertical page, alignment (centre, left, right) & list of files processing.
In our tests the processing speed is upto 34 times quicker than Adobe Acrobat 7.

simple command line parameters:

e.g. PdfImageStamp -iin1.pdf -ooutput.pdf -jimage.jpg (would stamp image, bottom left)
e.g. PdfImageStamp -iin1.pdf -fc:\ -jimage.jpg -pos10,10 -flipv (would page number stamp, top left)
e.g. PdfImageStamp -ilist.txt -fc:\ -jimage.jpg
list.txt file contains:-
in1.pdf
in2.pdf
in3.pdf

see full list of features for full list of parameters.