If you are using an Android device you can save and view your PDF patterns in your PDF viewer, usually File Commander.
Once you have signed into your account on LoveKnitting or LoveCrochet you can find your patterns in 'My Pattern Library'. Click on the pattern you would like to download and it will open in a new tab. Your pattern should also save automatically to your phone.
Next time you want to open your pattern, open File Commander and select Downloads, and you will be able to view your pattern again.