Quite a workflow you have here!
With the software and hardware you have now, maybe you can diminish it a bit, here are two ideas:
1 - crop what you want correctly when scanning. For each page preview first, then adjust the scanning window to the final size you want and then scan. You will be spending twice the time (at least) scanning but after having the tif files it’s just one more step - build the pdf (ocred or not);
2 - with your scanner you have received several pieces of software. One is finereader 5 sprint. Install it and se if it has an option to crop the images after loading them into the program (finereader 9 as it). It’s a great functionality (with the straightening function on loading, who aligns inclined scanned images) and permits, in a very fast manner, to crop everything up to the point one wants (this is what I have used to create from your files books1 and 2).
Finnaly, you can check the several programs that permit one to crop images or pdf’s that several people have posted about in the forum, specially in the pdf zone of the forum I think.
Wish you success with your endeavour, and remember, even if it takes time, once done it’s done for good, you will have not just the pdf for the DX that you can use now, but also a matrix document you can come back in the future to convert it to any other file format you want when the need comes - new reader, etc…