ResizeMe is a free, lightweight, yet quite powerful batch photo editor. It has a well designed interface and many interesting effects to choose from.
ResizeMe was able to open a PDF file for editing. The "Results" screenshot shows the final version of all manipulations I've done with it. I only spent like 10 seconds on it, but it looks amazing! There are only six transformations available, but you can do great things with them.
This program is absolutely free and it is designed to accommodate batch editing of files. I believe, this program would be extremely useful if you have your own website and you want to put up some pictures of yours in an album - this program is exactly what you'd use to do so. On the other hand, you could edit some pictures to create some collages with added captions (watermarks) and cool effects like mirroring, as shown on "Editing" screenshot.
Bottom line: it's free, it has many useful features and effects - I am going to put it on my watch list - in case I need something like this in the future.