You can use a Kofax signature pad in Citrix sessions using the Kofax SPVC signature pad channel. The Virtual Serial Sign Pad method is no longer supported.
On the Device
Connect the signature pad to one of the device's USB ports.
Go to Sessions > Citrix > Citrix Global > Mapping > Device Support.
Enable Kofax SPVC signature pad channel.
On the VDI Server (Windows)
Install the required software from Kofax.
The driver contained in this software will listen for signature pads on a virtual channel. Applications such as SignDoc will be able to use the signature pad.