You can only have One Budget at a time in AccKnowledge. As Ann mentioned you can setup multiple Forecasts.
Scanning directly is not possible from Macintosh because the OSX client from Citrix does not support Twain Connectivity. This unfortunately is a limitation of the underlying software architecture and is not under the control of M3.
You can of course use the Scan and Upload option to attach files from a Mac to Invoices or Journal Entries in AccKnowledge. If you need assistance with setting this up or attaching through the Browse and attach option, please open a case and a technician will contact you as soon as possible.