When you add the option to upload files in your configuration, a download button becomes visible in the Portal. With PDF files a user can download the file and than open it with the PDF viewer that is available. In most cases that will be a browser and downloading the file first might be an unnecessary step. So in the upcoming release we have added a PDF previewer.
If you go to a screen that has a download button, a preview button will also appear in case the file is a PDF, PNG, JPG or GIF.
By clicking the preview button, the previewer will be opened showing the selected file:
This option makes it faster and easier to read documents on screen. If the user prefers to download the document, that is still possible. And you don't need to change anything in your configuration.