No, you most definitely shouldn't. Attachments are a concept separate from your POCOs. You should store the attachment ID as string with your POCOs, if at all. Having a byte[] property in your POCO will bloat the document unnecessarily.
My advice would be to skip attachments and store binaries on the cloud instead - this is also what I wrote in that doc you referred to.
But if you are going to reference an attachment from a POCO, do this using a string reference.