In early 2019, Google began testing an option in Google Drive’s web version that lets you make all file types such as PDFs, images, office Microsoft Office documents available for offline viewing. Now, that feature has come out of beta.
Pursor.com is a free social bookmarking platform for free to use. Anyone can submit their content with links to this portal. It is a great place to get quality links for your sites which could help you to index your pages for search engines.