Question: I have a PDF with Type 3 font embedded. How can I convert this Type 3 font to Type 1 font?

Answer: 
It's been many years since this was asked, but I'm posting for anyone else that ran into this problem (like me). The best solution is to regenerate the PDF with settings to avoid type 3 fonts. For example, if you make your figures with matplotlib, then you can follow the instructions here: <http://phyletica.org/matplotlib-fonts/>

If it is not possible to regenerate the PDF or would require too much time, I also found that the using `convert` (found in `imagemagick`) can help. As others have stated, you may lose information, but this will work in most cases: `convert example.pdf example.pdf`
You may not be able to; Type 3 fonts can contain any PostScript; Type 1 fonts can only contain a restricted subset.