We implement a lot of on premise and hosted Citrix / RDS environments and one of the many issues we have to tackle when adopting an aging customer infrastructure and migrating them to a Cloud Desktop environment is the issue of document scanning. We find that many service based businesses depend on locally attached scanners for much of their business operations which makes migrating to a thin client configuration tricky. Scanner redirection together with old but otherwise functional scanners can usually prove to be buggy and unreliable at best.
There are many products on the market that help rectify this issue, most of which are cost prohibitive to implement. One that we have begun utilizing in many of our Citrix / RDS environments is TS Scan from Terminal Works. It has proven to be reliable with a majority of scanners utilized by businesses in our customer base and the licensing options that they offer enable a level of flexibility that helps by picking the most sensible model for their deployment topology.
They offer a trial for all their products which can be downloaded from their website: https://www.terminalworks.com