Yes and no. The issue is that Varnish is doing what it's supposed to do :) Caching static files! We want it to cache pdfs, and the URL format of "file=" is way too broad and would cause us to break cache for everyone which would not be a great idea. Instead of causing a problem for one user, we cause a problem for ALL users. Similarly, allowing file_uploads (which is where it stores the files) would cause serious slowdowns for others.
So I have to present you with some options!
Options one - Open a ticket with DreamHost and ask us to make you a Custom VCL rule to allow those specific URLs to skip caching. If you do this, please remember to give us the FULL URL of one of the files :) That helps us craft a specific rule for you. It may take us a little while to perfect it, but we certainly can do that.
Option two - Ask the plugin dev to do a couple things:
First - Put in a &nocache option in the plugin to bust cache. This will allow for more than just DreamPress to handle the files, as that's a standard call :) It would obviate issues with most caching systems.
b) Use pretty URLs instead of
file=folder/filename to access the files. This will allow us (and everyone else) to customize rules a lot more easily.
Option three - Ask the dev to make a custom filter so you can add on variables to the URLs. This is actually a good idea anyway, as it would allow you to put tracking analytics on URLs that don't call things like Google Analytics (since they're files and not PHP calls).
Option four - If you're not using their insert code and instead are making the URLs manually, just add &nocache to the end. That one I don;t like at all, but hey, use cases are special things!