No, you can't download Olympus Viewer 3 on the iPad because the software was not developed for iOS operating system. The software is available for Windows and Mac operating systems. In the image below you will see the exact system requirements you need to meet in order to install the software.
Download page: http://support.olympus-imaging.com/ov3download/index/
Note: If you simply want to download the file on iPad, access the page, scroll down and save the packages with Safari.