I'm using the beginners guide for B4A extensively.
The bookmarks in the PDF (Beginners Guide.pdf, Edit 1.3) is messed up.
When I open the bookmarks, I see things like _Hlt302172888 or _Toc301562001 instead of the bookmark texts.
It is nearly impossible to navigate in the document without the bookmarks.
I see the same thing. Many (but not all) of the bookmarks are in the form "_Toc301562044". It looks like they were computer generated names.
You can use FoxIt PDF Reader (free version) to change the bookmarks to the header names. Just click on the bookmark in the bookmark pane and press F2 to rename it (copy and paste the header name)