dobe Systems made an eye-widening play Monday, offering $3.4 billion in stock for rival Macromedia, which, if approved by stockholders, will move Adobe more fully into the developer marketplace and give it critical access to—and control over—one of the most widely accessible desktop runtimes, the Flash Player.

While the full details of Adobe’s plans—including the non-trivial issue of how it will handle competing, duplicative product lines (see Table 1) in the long term—will be revealed over time, it’s clear that the ubiquity of the Flash Player is an asset that Adobe can leverage in its efforts to transform the PDF file format. The company has already undertaken to reinvent the PDF format, offering interactivity and the option for developers to use PDF data and documents as part of a larger application, reading and writing data out of PDF forms. Supporting PDF through a programmatic platform opens up a new realm for developers, but allowing that interactivity to be delivered via the Flash Player would give end users the ability to take an end run around the heavy and staid Acrobat Reader.

Table 1. Macromedia and Adobe Product Overlap
For the time being, Adobe plans to continue offering Macromedia products under the Macromedia brand, but several products in the companies’ lineup are closely competitive.

Already many analysts and industry experts are pointing to this merger as an opportunity for Macromedia to seriously threaten Microsoft’s plans to dominate in the delivery of rich Internet application (RIAs), using the XAML-fueled Avalon UI technology under development in Longhorn. While Macromedia has already made considerable headway in this segment (the company’s Flex product already provides a server-side environment for creating RIAs that use the Flash Player on the client side), Adobe brings two significant additional assets to the battle: a considerable base of enterprises that would see great business upside in bringing their static PDF assets into an RIA environment; and money.

Even better, RIAs deployed via the Flash Player are inherently cross-platform capable, while Microsoft’s efforts are primarily tied to Windows. But while Adobe can certainly advance Macromedia technology and improve their power play, ultimately they’ll have to offer compelling reasons for developers to choose Macromedia technology over the native Windows environment and powerful development tools Microsoft already offers. Those who require platform neutrality already have such Java-based alternatives as Nexaweb and Sun’s open source JDesktop Network Components.

Adobe and Macromedia executives are betting big on the ubiquity of Flash and a broad dependency on PDF to fuel a footrace against the oncoming Longhorn juggernaut. But with both companies having grown up on the patronage of small business customers and individual developers and graphic artists, they’ll have to manage the details of this confluence very carefully, lest they pursue growth at the expense of their bread and butter.