When clicking on an attachment in an issue, if the attachment is an image, it opens up in a pop-up window and can be closed via the "X" in the upper right corner. If the attachment is an MS-Word file, it is downloaded. But if it is a PDF document, it is opened in the current browser tab. Then, to get back to YouTrack, we must click the browser "back" button. We'd prefer if PDF's opened in a new browser tab.