The Adobe Reader and browser plug-ins are still the standard. Yet there's plenty of room for improvement, especially when purpose-driven viewers can more nimbly display, for instance, engineering PDFs or long, text-based documents than the Adobe tools—which must be all things to all people, good for many things but superior at none.

Enter the alternative online PDF viewers, including: Google Docs, lightning quick; Scribd, a document-sharing site that launched a couple years ago; and this year's smart new entrant to the market, Issuu, which has offices in Denmark and the United States.

Issuu's main claim to fame is its elegant interface. Martin Ferro-Thomsen, Communications Manager of Issuu.com, says that, while the site's for everyone to use—and socially interact with one another while sharing content—its creators works hard to attract original content from copyright owners, as opposed to promoting a place where people upload bootleg copies of the latest Harry Potter book.

"Issuu just looks and handles better, and it makes your content look just a great as if it was published in a real world magazine," he says. "For anyone who's ever experienced the almost magical thrill of receiving the first copy of something they published, fresh off the press—that's what we wanted to recreate online."

That's the thing about PDFs online, there are many different classes of them: Staid government forms and lifeless court documents on the one end and on the other Flash-animated brochures, gorgeous color magazines, catalogs, and ebooks.

Issuu.com deals with this document dichotomy by offering two viewing modes: Paper, what Ferro-Thompson describes as a "PDF-like mode," and Presentation, tailored to photo catalogs and PowerPoint files. Issuu also recently launched Platform & Services, a developer tool for content owners to control how their pubs look—and unveil themselves—to readers.

"Right now you can completely customize the way the Issuu viewer looks," Ferro-Thomsen says. "We're expecting a lot from that, as this is really a way of empowering companies and publishing professionals to create their own vision of what an online publication experience should be."

Issuu has obviously hung its hat on PDF; that's the only file format the site accepts for upload. Ferro-Thomsen and his colleagues feel strongly that—for serious publications—it's the obvious choice, and will be here to stay.

While other file formats may do one particular thing better than PDF—image compression, for example—PDF is the standard that everyone can view on their computers, and even if a future digital file format comes in vogue he believes that there will still be an "export to PDF" button so viewers can email files and mark them up. Print fidelity and universal acceptance have driven PDF deep into the market, and Issuu's betting it's here to stay.

"Anyone [who's] visited a print shop or worked in publishing will know how immensely important PDF [is] when it comes to ensuring the right look in print," Ferro-Thomsen says. "That's an important part of the origin of PDF and that probably won't change any time soon."