您必須保持當前SDK版本的授權與更新，以便繼續(xù)獲取Viewer SDK不斷的更新升級。因為目前Viewer SDK處在發(fā)展階段，每月都會增加一些特性和功能，如：假如您現(xiàn)在使用PDF-Tools 版本3（版本4已發(fā)布），現(xiàn)在您需要升級到版本4，才可獲得Viewer SDK的授權。

現(xiàn)有3款完全不同且可用在開發(fā)者應用程序中的PDF瀏覽產品-以下兩者中可分開購買- 或者購買包含以下兩者，類似于捆綁選擇的PRO SDK。

Simple DLL SDK（已發(fā)布）所提供的函數(shù)集使開發(fā)者可以在其應用程序中嵌入窗口，實現(xiàn)PDF文件的瀏覽/打印。無論是圖形用戶界面的設計還是要采用所提供的哪個功能方法都由開發(fā)者決定，并且在開發(fā)者的產品中無可見的Tracker。

該ActiveX SDK（已發(fā)布）是一個功能齊全，并可與供終端用戶所使用的PDF-XChange Viewer模版相合并，還可在應用程序中嵌入窗口。開發(fā)者可以隱藏并使SDK中的大部分控制器和功能不可用，并且能修改GUI。但是存在軟件品牌跟蹤，并需要從嵌入瀏覽器的’About’窗口中獲取。ActiveX比Simple DLL擁有更多的功能特性。

Your existing SDK version license must be maintained as current and up to date to continue to access progressive upgrades to the Viewer SDK, as its very much in its development stages at the moment with new features and functionality being added each month - e.g. If you currently have PDF-Tools V3 (V4 has just been released) you will need to upgrade to V4 now to receive a Viewer SDK License.

There are 3 distinct products available for the inclusion of PDF Viewing within the developer's Software application - either of the below maybe purchased individually - or a PRO SDK containing both items below as a 'bundled' option.

The Simple DLL SDK (available now) provides the developer with set of functions to create a means to View/Print PDF files within a window embedded in their software application. Both the GUI design and means of employing the provided functionality is very much left in the developer's hands and no Tracker branding is visible within the Developer's product.

The ActiveX SDK (available NOW) option is a fully featured, ready to incorporate facsimile of the End User PDF-XChange Viewer, again embedded within a Window of the application, the developer is able to hide and disable most of the controls and functions within the SDK and some GUI tailoring is possible - but Tracker Software branding is present and required from the 'About' Window of the embedded viewer. The ActiveX is also more feature rich than the Simple DLL method.