When you're dealing with a tight deadline, an important deliverable and uncertainty, it's good to try every means possible and not assume that method will work. If the urgency isn't so great, or the deliverable isn't so important, you can hold back a little.
Things I'd do in this situation:
- If printed copy is how you always deliver it, then do put it in the most obvious place. Under the door is fine. It wouldn't hurt to put it in a manila envelope or a file folder in case of it getting stepped on.
- Shoot an email copy to him as well - that way he's got multiple copies.. it costs nothing and provides a great backup.
- Give a call to his cell if you've got it saying what you did. That way if he's left for the day unexpectedly, he knows where to look.
- Leave a sticky note on the door saying "you were out, I slid the copy under your door" and include your name.
The next time you see him - confirm that he got it, apologize in case all of this was annoying and ask what to do the next time this happens.
Thing to avoid: Don't ever ask if he's capable of bending down and picking it up. Ask "what's the best way to handle this next time" - that way, if he DOES have problems picking stuff up, he can come up with a clever alternative without admitting the problem.
This ought to work for anything that is slightly sensitive but not massively private.
I'll say I dislike some of the other alternatives on this question because:
- Jamming a document in the door jam often leads to the document falling off, or getting lost or damaged when people walk by.
- Don't fret about the janitor - chances are good that if he can get in, there's enough valuable stuff in there that the janitor would be a risk regardless of the document
As a last note - if you have strong confidential information handling procedures - follow them. Do all of the above EXCEPT shoving the document under the door. Lock it up by whatever means works, and then tell your boss where it has been locked up. If you are the only person who has access to the secure storage, give your boss the best contact info for yourself and prepare to come back to the office to help him if you have to leave.