When you upload a file in Drupal with the same name as an existing one (e.g., filename.pdf), Drupal automatically renames the new file to prevent accidental overwrites — resulting in filenames like filename_0.pdf, filename_1.pdf, and so on. This behavior ensures that files with the same name don’t unintentionally replace each other, which is especially important in environments with multiple editors.
Best Current Solution:
To effectively "replace" a file, upload the new version using a slightly different name, then update any links to point to the new file. There is a contributed module that supports true file replacement, but changing the file name and updating the link is the simplest method without added tools. We can add this to our list to revisit post-launch.
Important Note About PDFs:
Whenever possible, avoid uploading PDFs for web content. Instead, convert the content into an HTML webpage. This improves accessibility, works better on mobile devices and ensures users always see the most up-to-date information — especially important if someone bookmarks the page.