+*Another update (2023):* Marcus notified me that it is possible to use
+ImageMagick's `-compress jpeg` option, this way we can leave out the
+intermediate step and convert PNM to PDF directly:
+
+ $ convert image*.pnm -compress jpeg -quality 85 output.pdf
+
+You can also play around with the `-quality` parameter to set the JPEG
+compression level (100% makes almost pristine, but huge images; 1% makes very
+small, very blocky images), 85% should still be readable for most documents
+in that resolution.
+