Ensure to copy your n8n workflow and paste it in the code block, that is in between the pairs of triple backticks, which also could be achieved by clicking </> (preformatted text) in the editor and pasting in your workflow.
```
<your workflow>
```
That implies to any JSON output you would like to share with us.
Make sure that you have removed any sensitive information from your workflow and include dummy or pinned data with it!
I have run test on 1.72.1 and it works fine for me. You are using /tmp folder. It is meant to temporary location.
Could you try either Execute Command node or Docker itself to make sure the file is present before trying to access it with Read Files from Disk?
I actually got this to work. Instead of a PDF, I tried with a text file with no problem. It had to do with my PDF. Since I am trying to link up Paperless NGX, I pull the documents with the REST API now.