Should I sign office birthday cards, when I didn’t get one myself?

No, don't.

Oh, Christ on a stick. Get over yourself.

Etiquette, where you’ve posted, says that you sign them. Of course you sign them.

Then you change your diaper and stop thinking it’s funny to post this kind of thing. It’s not funny, it doesn’t upset anyone, it doesn’t matter. It’s just a waste of time and space - both of which useful things could be pondered in. Useful things like roadkill, stink bugs, and family embarrassments.

Nope

Get over yourself and sign the darn card! So, your co-workers didn't get you a card for your birthday. Big deal! Your birthday is no earth-shaking event!!
Did your birthday fall on a weekend? If so, that's probably why you didn't get a card. You wouldn't be there to receive it.

You should have enough brain matter to make that decision all by your widdle self but if you can't call your mommy and ask her since she clearly didn't teach you sheet!

If u do not want u do not need to do anything. Do not sign them, i also dont think the birthday girls will even notice

it depends on you.

Yours probably made the rounds as well. Then got mislaid. Most folks probably assume you received it. Of course you join in! Your card could be under the seat of the secretary or was mistakenly tossed out by the janitor. There is no reason to assume you are sorted out to be intentionally slighted! Get yourself a card if you feel badly and write yourself a love letter. You likely deserve something nice. It's just that no one knows you never received one.

Id sign them, it may have been a genuine oversight your birthday was missed. Next year publish the date of your by invitin them out for a drink.