"I think they have recently made it free of cost for a limited time offer. Previously, it used to be charged. Refer to:
https://www.ukvcas.co.uk/additional-services/detail
“Document scanning
If you are applying at a Core Service Point, UKVCAS can scan and upload all of your supporting documents for you during your appointment. Simply select how many people in your group require the Document Scanning service when booking your appointment and bring all of your documents with you to the service point. UKVCAS staff will scan everything in front of you and give you back all of your documents once complete.
It will speed up your appointment if you come with your documents already grouped by applicant and ordered by category, following the checklist provided to you by UKVI. Please also remove any staples or paperclips.
Complementary package
If you have booked an appointment at one of our Enhanced Service Points or Premium Lounge, or are using a Mobile Pop-up or VIP visit service, the Document Scanning service is included as part of that appointment.
Price
You can select the Document Scanning service for each member of your group when you book your Core Service Point appointment.
There is currently no charge for this service for a limited period of time."
this summarizes it nicely! thanks