As suggested in Vincent's answer, the easiest is to convert your PDF to images and I want to post another method that is very quick to do it.
You could also lock the editing capabilities of your PDF but the rectangles around your images will still appear when selected.
Quick way to flatten or convert an entire PDF into images
1) Do your PDF a you normally do and export it the same way as usual.
2) Open it in Adobe Acrobat Pro and find the tool option for "Preflight"
3) In Preflight, create a new custom "fix up" by clicking on the top "Options" button
4) Select the "Create new preflight fixup" option
5) On the left side of this new window, select the option "Pages" to see all the fixups relative to PDF pages. Then select "Convert Page into Image".
You can select your image resolution on the bottom part of this page before clicking "OK". Your images will be converted to that resolution. I think It's better to leave it at 300dpi and optimize the PDF with the trick on the link at the bottom of this answer.
6) Then simply select this new custom fixup, and click the "Fix" button at the bottom. The resolution should be the default one you chose and you can always optimize your PDF to lower its size because it will be heavier with all these pages converted to images!
All your pages are now images in your PDF!
You can use again this preflight fixup for your next catalogs; the custom fixup will be saved in your preflight options. You'll only need to open Preflight and then click the Fix button!
Here's a link how to optimize your PDF to lower its file size. Be careful when optimizing the PDF and selecting the right options; some will remove your hyperlinks if you have any!
To remove blank pages in Adobe Acrobat Pro PDF
Follow the steps above and select the "remove empty pages" in the "pages" or "fixup" sections.
Then save and use that fix-up on your file.
I think there's also a default "fix up" to remove them and you might not need to create a profile for this.