Hey Anna,
For the security of a file, when you upload a document using our plugin we save it in a secure folder to disable direct access. This is why when you click on download link the PDF is downloaded.
While this won’t always work, would be to upload the PDF using the “Media” menu in WordPress and then copy/paste the file URL in our plugin and also check the “Redirect to File” option for the download.
I hope that answers your query. Let us know if you have any further questions.