Swiss service provider seeks document management system (DMS)

I am looking for a document management system for my service company (business brokerage, accounting/finance) that can be connected to payment software and accounting.

The DMS should meet the following requirements:

• OCR text recognition
• Full-text search, ideally also within documents
• Tagging documents for easier retrieval
• Drag & drop import from MS Windows and/or Linux
• Workflow automation
• Integrated accounting or connection to existing, simple accounting software
• Connection to international payment software CLX Switzerland
• Transfer documents directly from iPhone app to DMS via USB cable
• Ideally with project management functions or connection to a project management system
• Optionally usable with Nextcloud (open source private cloud)
• Usable without a server
• Mobile application (app)
• Local installation or, better still, private cloud
• Simple solution
• Inexpensive, as it is a “one-man operation”

One to two software workstations are planned.