Welcome to Seven Forums albetkao. I found this, see if it helps:
This may be the way to do it:
1. From the CHM Menu click Options
2. Click Internet Options
3. From Internet Options window click Accessibility button
4. Check box Ignore font styles specified on Web pages
5. Click OK
6. Click Fonts button and select the font you want
7. Click OK
Also in the changelog for ver. 3.6 (looks like they are up to 3.6.5) I see this:
New "Choose Text Size" option for Internet Explorer publications (and new AllowModifyTextSize property in User Interface): you can let your users increase or decrease the default font size in pages.
A Guy