I’ve read conflicting info about sending documents using USPS. Can all docs be sent certified? and is there a way to send mail/docs registered postage paid?
The difference is the sticker. Green Certified Mail sticker, or red Registered Mail sticker.
Registered mail is more secure and is insured. It is the post office's most secure form of delivery.
If you send it Registered Restricted, there is a higher probability that the actual person addressed will get it instead of an office worker. Some post offices will not hand out the Registered Mail stickers ahead of time. Keep going to different POs until you find one that will hand them out.
My opinion is to use Certified return signature non-restricted delivery, since notice to the agent is notice to the principal and notice to the principal is notice to the agent. Use Registered return signature restricted delivery when you want to send it to a specific officer/employee.
To not send it through the USPS, place your mail in the blue drop boxes. Do not go into the USPS section where the workers are or you will be going through the USPS and will have to pay their fees. Some post offices will not recognize the free postage and will send your mail back to you requesting postage. Go to a different postal zone until you get one where they send your postage free mail.
You can use the same First Class Mail label used with the Certified mail. If you need these labels, I have the PDF.