[barium]

For anyone who's curious about this, now or in the future, here's one solution. It requires three free applications (god bless the developers), assuming you have scanned pages in an image format: ScanTailor, BRISS, and PaperCrop. It also requires a little bit of manual work, which is well worth the trouble. If you read a bit about each of these applications, you should be able to figure out how to format a non-OCRable PDF for viewing on a PRS-350. Briefly, here are the steps:

First, use ScanTailor to set margins so that they fit detected content. Use the other features as necessary (e.g. deskew). This is an oustanding application. The developer has posted a 20 minute video tutorial explaining the features in detail.

Next, if ScanTailor's content detection process leaves you with margins that are wider than necessary (for me page headers and footers that were set far from the rest of the text caused this problem), use BRISS to do a batch crop. Depending on your source material, you may need to draw several or only a few crop boxes.

Finally, use PaperCrop to split the pages in half. This does gracefully what Acrobat's tile printing feature couldn't do (that feature is designed for a different purpose). One problem is that it can resize your text a bit, which reduces its quality. I'm trying to figure out how to prevent resizing.

Thanks again for the suggestions and help.

Edit: changing the device resolution in PaperCrop from 800*600 to 720*550 helps the text distortion a bit, but it's not perfect. Does anyone know the resolution of the PRS-350 display in pixels? 800*600 is the screen's actual resolution, but I think its effective resolution is lower because of the status bar.