Fix add pdf upload file function to joomla component

We have a completed website that is using a component that the developer has abandoned us on, and one function that is broken is the ability to upload a pdf file from the admin view editing an item of the component, store the file on the server and database (a table exisits in the db) and then show a link to download the pdf from the front component view. The front view has a view override in place to remove the file download as it is not working. The current situation is that the component will not upload and save the file and complete the database entry. The developer said it is fixed but it clearly is not. Looking for a Joomla specialist to look at our component, understand what we have done with the override and fix or re-write the upload file function within standard joomla and secure php requirements to make sure it is all working. Thanks.