[TYPO3-english] How to handle file uploads in the Backend ?

[mardz iop]

I have to implement a "Book" management in the Backend. Each book has a PDF preview, a title, description and so on... The BE user should be able to upload a PDF and set a title, description etc. through a Backend module.

I don't know how to handle the upload part in the backend. I didn't find much info online beside this upload example: github.com/helhum/upload_example

I tried to implemenent it but I get this error when I submit the form:
#1297759968: Exception while property mapping at property path "image.error": No file reference (sys_file_reference) was found for given UID: "4"

I'm not sure if this is even the right way for this task..