I found that in some cases, LaTeX produces bold-type text throughout an article when creating a PDF file using dvipdf or ps2pdf. In such cases, the DVI or PS file will look fine, but the PDF file has bold face everywhere. The reason probably lies in the options with which ghostscript is called to produce the PDF files. I am not sure to what extent the LaTeX source and/or style is important.
The solution here is simple: use dvipdfmx rather than dvipdfm or dvipdf. I surmise the reason that this works is that dvipdfmx uses one of the -dPDFSETTINGS described below (editing the dvipdf script on my system and adding that option (after the option -sDEVICE=pdfwrite solves this problem as well).
If you’re producing PS and then use ps2pdf (or e.g. ps2pdf14), the same may happen: while the PS file shows regular fonts, the PDF file contains bold type only. Clearly this is caused by ps2pdf.
The solution in this case is to use
This tells ghostscript to produce higher-quality PDF. It may also use fewer standard fonts, which means that the resulting PDF file will slightly larger, since more non-standard fonts need to be embedded. The default option is -dPDFSETTINGS=/default which probably defaults to -dPDFSETTINGS=/screen, which gives a sub-obtimal result.