Hi 450224,
Welcome to the HP Forums.
I see that you had a paper jam and want to know how to remove it.
I will be happy to help you.
I have provided a document to go through the steps to see if it will resolve this issue.
Clearing Paper and Carriage Jams.
The back door isn't supposed to be a removable part.
If you are still in warranty I would recommend to call HP Tech Support for further assistance. Contact HP Worldwide.
If you are out of warranty, there is a blue plastic piece on the bottom of the printer that looks like it can be removed. You might be able to remove the paper jam from that area. Do this at your own discretion.
Hope this helps.
Thank you for posting on the HP Forums.
Have a great day.