May I suggest to port DocFetcher to ARM CPUs so it could run on eg. Synology and QNAP NAS devices. There could be a daemon that updates the index regularly or on changes in the filesytem.
This would allow to run DocFetcher 24x7 in a kind of a sent-and-forget-mode. PDFs and other docs are copied by the user to the network share hosted on the NAS.
When searching, the user could either use a web interface (when available) or launch DocFetcher App from that network share. Indexes would be up to date then.
Sorry, there are currently no plans to support such devices, with the main reasons being:
This feature would require a lot work.
The feature doesn't seem significant enough in comparison to the endless list of other possible features (where "significant" is to be understood in terms of number of users who would find the feature useful).