Fonts turning bold once exported as a PDF from Illustrator and InDesign?

Hi there,

I've been having a weird issue that I see other people have had in the past without finding a solution that works for me. I'm creating a single combined PDF with exports from both InDesign and Illustrator with the intention of uploading it to my website and sharing it with others via email.

When I export it and view it personally, the fonts all look normal. When I upload it to my site, a lot of the font turns bold, but not everything. Someone else also asked about it when I emailed it to them - the bolding of random lines of text.

I've read that sometimes it has to do with transparency effects throughout the document but I have no transparent objects. It's just text and vector shapes.

Any help or info would be great.

Thank you!