I have taken the liberty to download the file you have put in rapidshare, hope that is not a problem.
First of all let me check with you if the file does not contain corrupted tif files.
They are 6, scanned in grey at 300dpi, but all show a black bad part under each oneÖ is this what you intended?
Iím posting here a pdf of page 3 for you to check.
Anyway, my advice.
1 - check the Plusteck 3600 scanning software and limit your scan area with it, you will save lots of time and get the almost perfect page size so you will not need to crop the image later or if so you will have to do it just a bit;
2 - do not scan these types of books in greyscale, itís too much information for nothing, 300 dpiís at black and white is perfect for it;
3 - if just using Acrobat to produce the final pdf (what version do you have?), apply a final compression to the file using (in Acrobat 8 here) advanced/pdf optimizer and check the parameters there before compressing, per example in this situation you should have for the Monocrome Images option - Downsampling Bicubit Downsampling to 300 pixels/inche. For images above 450 pixels/inch and for the Compression option JBIG2 and Quality Lossless.
Iím putting here also what I have done with your tif images (6 pages, total 20.5 Mbytes), and the result is a 145 Kbyte pdf file(!):
1 - opened the tif files in Finereader Pro 9.0 converting automatically the files to black and white;
2 - cropped in Finereader the pages, mainly cutting the black bar I mention above;
3 - applied ocr to the files and saved the result in pdf format with 2 layers, above the image and under the text;
4 - opened the pdf in acrobat 8 and optimized itís size as I describe above in (3).
Please check if it works for you in the DX.