How to create a thumbnail from PDFs or various other document files?

What would be the best way to create a thumbnail image from a PDF or vario开发者_JAVA百科us other document files?

You might find some useful answers in this related question.

In general, you need to be able to "rasterize" the file format to a bitmap at the desired resolution. PDF is Not Easy to render (properly that is). Depending on what those "other formats" are, the difficultly could be anywhere between "trivial" (a bitmap format would just need to be scaled) and "Nigh Impossible" (some proprietary format... MathLab or some such).

How to do all that in PHP? Not really my department. But at least now you know what questions to ask (though none of this might be news to you).