How can I return to viewing a pdf in Polaris office after navigating to another app?

[AC Question]

Hi. If I use the native browser on my Samsung Galaxy S5 to view a web-page, and then navigate away from the browser to use another app (eg to make a phone call), I can return to the browser and carry-on reading the same web-page where I left off. By contrast, when I click on a pdf download on the web-page, the download opens automatically with Polaris Office; if I then navigate away to make a phone call, I don't seem to have any easy way to get back to where I was in the pdf. If I click the internet app I am returned to the web-page from which I downloaded the pdf, rather than to the pdf itself. There doesn't seem to be any Polaris Office icon on the phone, even though Polaris is obviously installed. Can anybody tell me how to get back to where I left off in viewing the pdf in Polaris?
Many thanks

 

[Jims S5]

How about going to your recently open apps button.