I have versions 1.6.1. The thing is so strange that I can't add pdf files, but not all. Some are added and others are not with the message "An error occurred, file attachment failed" On version 1.5.3 I had the same problem. I thought if I upgraded to a higher version the problem would go away. Unfortunately, that didn't happen. Anyone had the same and can help. The server it is installed on is synology.
PK
Not sure, but may be depend from file size ? Or file name (length or symbols) ?
I checked more thoroughly.
All files, not only pdf, regardless of the name, up to about 762KB are included, above 777KB are not.
Problem solved. Disabling the "database_attachments" plugin fixed the attachments issue