Private File System and Externally Modified Files I have a D7 site that includes a few hundred nodes that have PDF attachments that use the core file field and the private file system. The site uses a custom module to dynamically watermark these PDFs and we're going through an update that requires each PDF to be updated to use a new layout. 

In order to minimize downtime, what I was hoping to do was pull the site to a development environment, directly edit the PDFs that are stored in the private file system and then push the updated files and changes to the watermarking feature back to production. 

All seemed like a good plan, but I'm finding that Drupal will no longer serve the updated files after they've been modified. No error messages in the logs (Drupal, PHP or server) and the site just times out when you request new files from /system/files/...

I haven't been able to find any documentation or relevant issues on the subject, but I'm wondering if Drupal's private file system is failing to deliver the file due to changes to the timestamp or file size?

Has anyone run into this before? I'm hoping there's a workaround that does not require that we update hundreds of nodes by editing and manually re-uploading each file one at a time. 

Thanks much!
The files won't be served if the entry in the file_managed table for that file does not have the correct filesize.