I stumble across a lot of interesting webpages on a daily basis. Sometimes it's a video I want to watch later; sometimes it's an article I don't have time to read right away. Other times, I find a webpage that I want to keep around for future reference. For me, there's a difference between articles to read later and reference material: whereas a new item added to Instapaper has a short life span in terms of attention (read, share, archive), a webpage I want to keep around forever needs to be turned into a document I can read anywhere, highlight, annotate, and carry around between platforms and devices. For that, I like PDFs.
I keep a "PDFs" folder in my Dropbox that contains all the documents I check upon regularly for work and personal purposes. They can be eBooks, tutorials, or guidelines from Apple that are essential to my writing online. Thanks to the increasing support for cloud services in apps like PDF Expert, GoodReader, and iAnnotate, I can keep a single copy of a PDF in my Dropbox, use the app I want to annotate the document with, and forget about duplicates thanks to sync. Furthermore, I'm fairly sure that, due to their popularity, PDFs will still be readable and supported 20 years from now, so I don't have to worry about data preservation and file formats.
Lately, I have become obsessed with turning longer articles I find on the Internet also into PDFs for long-term archival. For as much as I like Instapaper, I can't be sure that the service will be around in the next decades, and I don't want my archive of longform and quality content to be lost in the cloud. So I have come up with a way to combine Instapaper with the benefit of PDFs, Dropbox, and automation to generate documents off any link or webpage, from any device, within seconds.
(Disclaimer: what follows is an explanation of a hack I created for personal use. It uses publicly available tools and apps to fill a personal need. You shouldn't create PDFs off websites and redistribute them -- you should support the sites you read instead).
In short, I use the Instapaper Text bookmarklet to fetch a webpage's text and images (while preserving hyperlinks and great typography) and I convert the resulting page to PDF using wkpdf. Created by Christian Plessl, wkpdf is a command line tool that uses WebKit and RubyCocoa for rendering HTML content to PDF. Since wkpdf uses WebKit's HTML rendering, it can generate good-looking PDFs that maintain most CSS2 and CSS3 stylings and properties. I have tried another command line tool for file conversion, Pandoc, but I like wkpdf better for straight HTML to PDF conversion.