I was hoping to be able to export the architect's CAD drawings and Excel spreadsheets as .pdfs to benefit from vector quality and small file size,

but for the time being maybe I'll need to export them as .png

Shai, in response to your question about the saveable checklists, these would need to act like an inventory of products, so there would be a series of items, each with a title, description, image, item code  and associated options to be checked / unchecked, as shown in this image: