If you want to test PDF download functionality with Sauce, there are two main issues Selenium:
- Downloading a PDF may try to open a PDF plugin, which Selenium can't access.
- Download dialogs are native UI elements, and not supported by Selenium.
You could try to work around these issues by changing your browser configuration to download PDF files automatically, as described here: http://elementalselenium.com/tips/2-download-a-file.
However, we don't provide access to the file system on our virtual machines where your tests will run.
If you want to test PDF download functionality with Sauce, you should download it locally: get the URL of the PDF link using Selenium, and then download the file using wget, cURL, or your favorite HTTP library.
This blog post has more information: http://ardesco.lazerycode.com/index.php/2012/07/how-to-download-files-with-selenium-and-why-you-shouldnt/