Printing/exporting messes up the document

I have a 67-page document with a lot of pictures too, and I use multilevel headings. When I try to print or export to .pdf, it messes up the whole document, I have now 102 pages, sometimes 92, the approx. 5000 word count is now 7000, and the order of the headings is messed up, so some parts of the document are moved across the document. What on Earth is this? I changed all the fonts to Arial. Tried every kind of printing setting. Nothing works.