Finally, we were able to solve the Arial Italic and Bold problems. Using Metalink Note 261879.1, it was relatively straightforward to add the font.
The steps to follow are:
1) Transfer the Arial fonts (ttf version) from Windows to UNIX. Make note of this directory.
2) Use the open source program ttf2afm to generate Adobe Font Metrics (AFM) files for TrueType (TTF) fonts.
3) Modify reports_path to add the fonts directory.
4) Make sure the AFM file for the italic version does not have the (-) sign for the slant angle.
5) Update the ALI file to add the Arial font in [PDF] section. Check the version of the ALI file mentionned in the Metalink Note 261879.1
6) Restart the reports server.
These steps can be used for any font that you want to add to your reports server setup.