Okay, here's how to scan-to-PDF on the cheap. It took some finagling to figure out how to do it, but it works.

1. Get a free internet fax number using http://K7.net (this clip).
   
2. Fax your document to yourself.
   
3. Download the .TIFF file from your email.
   
4. If the document is from a book, with two pages side-by-side, it will be oriented wrong (sideways) -- you'll need to rotate it 90 degrees clockwise. If not, skip to the final step.
   
5. Open the .TIFF in Microsoft Office Document Imaging (I know for a fact this program works. Others may, too, but so far I haven't had much luck).
   
6. Click Page > Select All Pages; then click Page > Rotate Page > Right 90° (or whatever is appropriate).
   
7. Save the document. It appears that for the new page orientation to be saved, you have to change the page compression. I don't know why. Do this using the "Options" button in the Save dialog. You may wish to rename it in case something goes wrong.
   
8. Close the file. Then re-open in the same program.
   
9. Click File > Print, select your print-to-PDF program (I used CutePDF), click Properties, and change the page format to Landscape.
   
10. Print it using CutePDF or other print-to-PDF program.
    

Voilà. A quick, free way to produce long (low-quality, image-only) PDFs from printed documents that doesn't involve standing in front of a scanner for half an hour. It took me like an hour and a half to figure out how to do this.