Historically, it's a very normal requirement → that this would be run as an update to existing content. This is easily done using Views Bulk Operations, where you can select all the affected nodes and simply bulk run any action that includes a "save" (I used "set published" as the least disruptive action, IIRC). All missing derivatives should get filled in at that time.
But updating many existing images after changing the settings is a little trickier. I would still look towards VBO if it had the option to Bulk edit/delete field → , because deleting an old image through VBO would still trigger the action of generating a new one immediately.
Long ago (drupal 6) there was a thought to publish an "Action" to let you directly "Update PDF Image". That would be the tightest approach, and most integrated with Drupal content admin. Back then, The work-around was just 2 lines of VBO PHP-action, so that feature was never published.
I believe you can also trigger actions like this with `drush vbo-exec` if you really want to do it that way.
OK, I've added
https://www.drupal.org/u/hitchshock →
as a maintainer on
https://www.drupal.org/project/pdf_to_imagefield →
now.
Vaya con Dios!
.dan.
Hi.
Sorry for not replying promptly.
As you may see, I've not been able to devote any time at all to my good old Drupal community for - several years!
So yes, have no current availablity or desire to maintain this module - the D7-8 upgrade gulf looked way too intimidating for me.
I will endorse this request, and go in and add you as lead admin right now!