The embedded type of PDF Flipbook is the basic and default viewer from DearFlip. These work great on page where the main page about the book or when these is just one book in page.
Example: Embedded Viewer in a Page
But things change when there are more than one flipbook in a single page. A single Flipbook consume certain amount of time to load and consumes memory. Thus multiple embedded flipbooks will increase that page load time and memory consumption additively.
So, we recommend using Lightboxes(Popups) shortcode solutions like buttons, thumbs, links.
Example: Popups and Lightboxes
What changes you need to do?
The default shortcode needs to be updated to popup shortcode by adding
[dflip id="123" type="thumb"][/dflip]