Disable .pdf caching

Hello @terry777

Thank you for reaching out and I am happy to help!
This requres just a small tweak in the settings. I am assuming that when you say you update the version of the PDF files, you are using the same name of the files and just re-upload the updated version?

Please let me know if this is the case.

If I am correct, the problem is with the Browser Cache and the cache-control / expires header. Since you havnet share the website URL, I cannot confirm this, however, if you go to Performance>Browser Cache, and scroll down to media&Other files section, you will see that the default Expires header lifetime: is 31536000 or one year.
This is a standared for static files and this means those files remain cached in the browsers of the users that visited the website, and this is because next time they visit, the browser will recognize them, and fetch the exisitng version so there is no need to download those files again!

This is easily solved with Cache busting option in the W3 Total Cache Browser Cache settings which you can find in the same sub-box “Media&Other files”. This option is called ” Prevent caching of objects after settings change”
What this option does is when enabled it adds the query string to the static files for example https://yourwebsite.com/wp-content/uploads/some-pdf-file.pdf?xNNNNN

This random query string is used for versioning of the files so that next time you update any file and update the query string, the browser will see that query string, it will not recognize it and iwll fetch the updated file from the server
Make sure to enable this option, save all settings and purge the cache. Next time you update the file, go to Performance>Browser Cache, click the “Update Media query string” button at the top of the page as shown in the screenshot below, save all settings and purge the cache

Please let me know if you need any clarfication and if this helps!

Thank you!