How do I spend on a paper wallet without compromising it?
imho best way is to download mycelium (
https://play.google.com/store/apps/details?id=com.mycelium.wallet&hl=en) and import it. anyway, use non-rooted "clean" phone, if amount is huge, I even recommend to buy new one just for this purpose. officially:
Partial spend from cold storage
Use this function if you would like to keep some funds on the paper wallet.
Download Mycelium from the Android Play Store or through iTunes.
Press the menu button and select "Cold Storage"
Scan in private key
Select your destination address
Select the amount
Press the blue currency tag at the top to toggle currency.
Send!
source: https://en.bitcoin.it/wiki/How_to_import_private_keys