How Scribd's HTML5 conversion works ... even when it shouldn't

Their entire business model involves displaying PDF content on the internet.

The fact they have to jump through hoops to achieve that, while potentially impressive, is a function of their entire RFB (reason for being... I just coined the term).

Whilst technically impressive, it reminds me of the 'NASA spent millions developing a pen that writes in space vs Russians used a pencil'.

Googles competing pdf reader just renders pdfs into images which also have selectable text.

I've put a few PDFs of presentation slides on scribd, and then used their widget to embed those slides directly into a blog post talking about the presentation. Linking to a PDF on another page (and asking many people to a) open acrobat, b) download a multi-MB file from my host) and/or hosting that PDF yourself is sub-optimal. Let scribd host it (you can provide a link to download the actual content you uploaded, rather than their web widget), and pay for the bandwidth. I never saw the use for it, until I started giving talks and wanting to embed them. It's youtube for PPT :)

Browsers are "smart"- they won't let you select text that's 100% transparent. 99% transparency works... but also looks kind of weird if the texts don't overlap perfectly.

You can roll your own text selection in javascript (on top of the bitmap) if you know the glyph positions though- that's what e.g. Google Books does. It's a valid option if you don't care about zoomability.

That's almost what Google Docs PDF viewer does. Each page is a JPG. This is served to the user with a catalogue of text layout then JavaScript is used to simulate selection and copying.

Yep, you can do just that. Browsers that support rgba for text color make it quite easy and in older browsers you can do onselect tricks and the like to make it work.

Especially since downloading is no extra step if your browser can display PDFs natively. (Safari can, Chrome will soon and I’m pretty sure there are plugins for other browsers.)

I’m using Safari and to me viewing PDFs is the same as viewing webpages. Heck, it’s even a bit more comfortable. (There is one big button with which I can open the PDF in Preview which allows me to rearrange/delete pages and to annotate and there is another big button which allows me to save the PDF for later reading.)

What Scribd does certainly is impressive, I’m just not sure how useful it is.

It's horribly confusing to someone who doesn't understand that it's not being rendered by the browser itself. PDF's (especially when rendered inside the browser) break the browsing experience.

Your browser controls stop working as expected, history gets bent, links don't work as expected. All of a sudden you're now working within an Adobe Reader application or FoxIt Reader (albeit embedded in the browser) without even realizing you're in an entirely different context outside of an HTML page.