Border around text box appears when converting to pdf

[katia_8445]

I converted my word document to pdf and black borders appear around text boxes which are on top of an object (circle), see screenshot. I did this a couple of weeks ago and only the text appeared. Now, borders appear where they shouldn't be there. Any idea what happened and how to solve this? I already tried to remove them and add them again but it's still the same. As it's for the layout of a book which needs a small revision, I can't start the document all over again.

n.