FX File Explorer is a great file manager. I've been using it personally for 10 years. It has split-panes which definitely come in handy as I've always used Galaxy Note devices. It has all the features mentioned.
What you are describing is a basic devops workflow. MS groups all of yve tools into a product called Azure DevOps, Atlassian (a competitor) splits then into separate (but interconnected) products.
It sounds like you are looking for the features of Atlassian's JIRA.
These tools do no read from PDF/doc files, you have to create projects and tasks in them, ...