* And I probably wouldn't align the text in the captions to the baseline grid. (A slight movement of the image+caption pair could cause the text to jump around trying to re-align itself and you end up trying to arrange the image to suit the caption, which is the wrong way round.)
This is very true.
I haven't looked at the document until now, the one thing that first caught my mind was: There are way to many indentations.
For the contents listing, there is both indent AND a dash. For paragraphs there is an indent AND space between paragraphs. I don't know know about dutch typography but in swedish typography you use indents OR space between paragraphs (and I prefer space, because indent shouldn't be used after a heading so using indents I need to paragraph styles), never both.
I also think there is way to much spacings after the different headings. A heading belongs to the text below, thus it doesn't make sense to separate it more than necessary from the text below. If the heading is bold there is really no need to have a larger spacing than the regular line spacing. Larger space before a heading may be useful sometimes (but when using the baseline grid you automatically get more spacing if the font size of the heading is larger).
I also think the font is a bit to big, making the lines unnecessarily short.
One single drop cap at the start of the text? Why?

The "in column" images have been mentioned before, that's how most people writing in word processing programs do, because they don't know anything about how you can "place images"

This documents looks a lot like a "Word document poured into three columns".
I generally try to place images "around" the text, rather than "in" the text.
Sometimes I use empty frames to force text to wrap.
Now, I recognize much of what has been pointed out is probably "beginner mistakes". I know documents I made 10 years ago look awful compared to what I create today, and then I'm still an amateur:). I have read books and web pages about graphic design and typography and learned a lot over the years, but I'm still learning. It's easy to learn how to spot mistakes, it's harder to learn how to avoid them:) I have also had many of my layouts criticized, and learned a lot from that too. So don't take all this as "you suck on design" but as "you can improve"

There are positive things to say too, for example there is not an excessive use of different fonts, there is a lot of air around the text.