k2pdfopt tool (hey, source code is also available) to convert the A4-size technical papers to formats suitable for Kindle.
Check the one example from the author's website: original paper => Kindle-ready PDF.
On Linux, it is usually one single command to convert the paper PDF to the version suitable for Kindle. My favorite option combination is:
$ k2pdfopt -dev k2 -as -x -ui- /path/to/your/pdf/file