Bookmark OS - Bookmark OS is like Mac or Windows optimized for bookmarks.
pdflayer - Free, powerful HTML to PDF API supporting both URL and raw HTML conversion. Unlimited document size, lightning-fast and compatible PHP, Python, Ruby, etc.
BookmarkSheet - Your bookmarks in Google Sheets
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
Annotate.tv - Optimize your learning on YouTube
Tcpdf - TCPDF: Open Source PHP Class for generating PDF documents