If you uploaded a PDF with links and they appear as highlighted in the flipbook, here is how to change that.
First, open the flipbook in the editor and go to a page with highlighted links. Next, left click in one of the corners of the pages and while holding the mouse button, drag it to select all the links on the page.
Once the links are selected, click on the Opacity button at the top of the editor and set it to 0.
Check out this article to see how to add links to your flipbook.