After introduction of PDFTRON we are relaying more in more in PDF files for view and comment.
Customer migrating from 2015 and lower versions are not yet used to have PDF as part of their current system. Also not much common for customer migrating from other system of from file systems.
Current solution can generate the rendition of those legacy documents following similar process as:
1- Create a separate rendition job only for legacy, so you can have a little flexibility to schedule it to run after hours and not interfere with day-to-day renditions requirements
2- Select all legacy documents (maybe searching for property RenditionUpdated empty) and send it to publisher queue. This step is really painful, it is not easy to select 200000 documents and run a command to send then to the publisher queue. Most likely you gonna have to do that splitting in 10000 docs junks or so.
3- Scheduled job for after hours.
It would be a great improvement if there was a specific legacy rendition job, where I could setup the rendition option (similar to existent update rendition job) and could select a collection of documents or just set something for RenditionUpdated property, like documents with empty RendtitionUpdated of with date lower than something. Then everytime this jobs run it will search for the documents in the collection or based on the RenditionUpdated criteria instead of look for the queue.