Only the pages with text+jpg are exported properly.
The pages with any other image type with some transparency, i.e. psd, ai, even png, have bold text after exporting to pdf.

It's an old issue, coming back every now and then in many InDesign editions in the past. So we all should know how to deal with it, shouldn't we? Well, here is the rub. The trick with the text placed on a separate layer on the top doesn't work anymore. Nothing works, actually. It's a major bug. A reason to downgrade to the last correct version. I needed to export a very important work today and I have spent most of my day trying to work this out. I have downgraded to CS6 eventually, just to be sure that it would work. And it did, but hey! This is not the solution.

Another workaround that I know of is to print your publication to pdf instead of exporting. But still. It is a huge bug and we need you to deal with it real fast.