[magicmicah85]

Never heard of needing to open a PDF in sandbox mode, but it makes sense cause of potential malicious content so I looked up if Chrome does it by default with it's viewer. It does, as does Firefox and Safari so that covers most browsers.

[SchemaLoad]

PDF in the spec contains an insane amount of stuff which could be exploited. But every reader other than the Adobe one leaves out most of the spec.

So I wouldn't be that worried about opening a random PDF in a browser. But I would be maybe worried about opening one in a desktop app written in an unsafe language.