Based on clemente's version, for my personal use. Changes:
Check for all papers even if there is an available download on Google Scholar.
Put the download button in the footer, this way it is less intrusive.
Add Preview button to preview in browser.
Flag davidgogh/Download on Google Scholar
Are you sure you want to flag this script for potential inspection by a Moderator?
Donate for the site OpenUserJS
Are you sure you want to go to an external site to donate a monetary value?
WARNING: Some countries laws may supersede the payment processors policy such as the GDPR and PayPal. While it is highly appreciated to donate, please check with your countries privacy and identity laws regarding privacy of information first. Use at your utmost discretion.