Thanks, Alex, I might give it a go.
Last night I downloaded a trial version of ABBYY FineReader 6.0 Professional
, which is an optical character recognition program which can convert pdf files.
I tried it on a sample timetable, but it didn't make a very good job of it. The problem seems to be that it's actually working on the basis of an image of the pdf page, and this particular image is very misleading as to where the column dividers are. However, I haven't read the extensive instructions and tutorials, so there might be a way to improve the performance.