The Export menu has options for
- Current Selection
- All Objects
- Specific Region
- Current Canvas
- Entire Document
But when you select multiple canvases in the Canvas sidebar, "Current Selection" is greyed out in the Export menu. When I want to create a PDF containing a selection of canvases (often), I'm forced to export the entire document, then delete the unwanted canvases in Preview, then re-save.
I'm sure you'll agree this is a much-needed feature.
And please, please, please, in your next beta, add canvas numbers to the Canvas sidebar. Make it a hidden preference if you must.