If the PDF doesn't display at all then please get in touch with our support team via email: firstname.lastname@example.org. Send a link to the page containing the 'broken' embedded PDF.
First, you may be able to diagnose the problem yourself - or at least find out some more information that could help the support team.
There are three possible approaches to diagnosing the problem.
1. Trial-and-error to find conflicting plugin/theme
In the WordPress Plugins page, try temporarily deactivating all plugins other than PDF Embedder, and switch to a simple Theme such as Twenty Seventeen.
Reload the problem page to see if the PDF now displays. If so, there must be a conflict with a Theme/Plugin. To find out which one, reactivate each one at a time and reload the page containing the PDF after each reactivation. When the PDF breaks again, you know which plugin/theme is at fault. Your next course of action may be to get in touch with us to explain your findings, or just switch plugins/themes if you are happy to do so.
If you are using a theme or plugin that enables you to create your posts using a drag & drop layout builder, such as Divi, Elementor, etc., please see the following tutorial: Using PDF Embedder with Drag & Drop Layout Builders
You may need to reload the web page.
If there are any messages in red, what do they say, and do they point to a particular plugin? It may not be obvious why the error has occurred, but in any case you can send a screenshot to our support address to help our investigation.
Also in Developer Tools (as above in 2), there is a Network tab that can show you which files are loaded into the page, and we need to make sure all the plugin's files are loading.
Once the Network tab is open, reload the page, then you can enter the text 'pdfemb' to filter the list of loaded files to those that might be relevant.
You should see at least:
all-pdfemb-premium.min.js (or -basic.min.js)
compatibility.min.js (no longer included in plugin with version 3.1.8+)
If some or all of these aren't listed - particularly the first one - then somehow your site is failing to respect the PDF Embedder plugin's request to include those files. Sometimes this happens if your Theme does not contain a wp_head or wp_footer section - which should mean something to your theme developer... As in 1 above, try switching to a simpler theme to see if that at least shows us that the theme was at fault.
In all cases, please just get in touch if you have a problem with the plugin. Send a link to the page containing the broken PDF embed, and any information gleaned from the steps above. Just ignore the steps if they are outside your comfort zone. We have listed them so some more technically-minded users can potentially diagnose problems without assistance.