Dedalus’ papwallets don’t contain full recovery info, you can see it in this demonstrating video:
Daedalus generates papwallet with 15 out of 24 secret words on it, so you need to print it out and then write additional 9 words manually. I reckong it’s a secutiry measure against possible hacks in between the Daedalus and a printer.
If you manage to edit the resulting PDF to add 9 remaining words to it - you may store the result on a USB stick. But I don’t understand the reason. Do you want to store it on a flash-drive permanently? If so - then it’s the same result as just putting your 12 secret words in a text file and storing it on the same USB stick.
Or do you mean just temporarily use USB-stick to transfer the wallet file (maybe to a printing facility)? If so - then yes, it would be safe because of 9 missing words, but then you would have to do it like this:
- Create papwallet in Daedalus
- Save resulting PDF file on a flash-drive
- Write additional 9 words on a peace of paper and keep it secure in secret
- Go and print your papwallet anywhere you want
- In some safe place write down you 9 words from the peace of paper onto the papwallet
- Destroy peace of paper
- Glue papwallet together and keep it safe AS IF IT IS YOUR MONEY
