The following are my thought on how one might survive a zombie attack in an office building. It is in no way definitive and following my advice on preparation could potentially get you in trouble with your boss if he/she doesn't realize the danger zombies pose. I cannot be held responsible if you lose your job, go to jail, or your death by zombies should my advice prove useless, etc, etc.
Worst case scenario: you're unprepared and the first sign of danger are screams and shrieks as zombies attack your less fortunate co-workers.
Naturally you'll want to procure a weapon. Since most offices don't allow weapons (particularly firearms) you'll have to make do with what you can find. If you're lucky enough to have them, a fire axe is a good choice. Lethal and easy to use with the stopping power you'll need. They are not perfect however; they could easily get stuck in a zombie skull or shoulder. The blade form a large paper cutter will have similar advantages and disadvantages but will be harder to use with two hands and offer less control and power. The legs from tables and chairs can make good blunt weapons if you can remove them quickly enough. They won't get stuck in a zombie but probably aren't quite a lethal. Obviously any solid meter long object will be sufficient. Your office kitchen might have kitchen knives which might be of some use but they have a short reach and won't easily cause lethal damage to a standard zombie. I wouldn't recommend any kitchen knife unless you have absolutely nothing else available I think you'd be safer with a metal folding chair.
You might be able to get your hands on a baseball bat from an office if someone is a big baseball fan. Golf clubs are probably a more likely find and will do in a pinch but they won't stand up to much punishment. If you were smart enough to plan ahead for this inevitable situation you'll have been able to sneak a bat in and have it stored in your office/cubical/work area, whatever. How you will accomplish this will be more difficult depending on what kind of office you work in but should be doable. A bat is probably the best weapon you could hope for in your average office, it's strong, damage resistant, easy to use, won't get stuck in the zombies, and it is a weapon that you might be able to keep in the office.
If you cannot find a weapon and there is no easy escape, you'll have to hide and cowering under a desk just won't cut it. Closets and offices might be the easiest places to hide but are also the most likely to be found by zombies. Since zombie intelligence is not a constant they could be able to manipulate door knobs, especially if your offices uses the knobs that are the lever kind rather then the "ball" kind. Even the dumbest zombies could accidentally open a door with the lever knobs. Additionally, office doors are pretty flimsy and won't stand up to much zombie assault. But if you do chose to hold up in an office, it goes without saying, don't pick and office with a window to the main office area.
Cabinets and Cupboards are likely safer as zombies are almost never smart enough to look in such areas. However, they won't be as comfortable and they won't likely have any latch. A less obvious option is to hide in the ceiling. Since virtually every office has a drop ceiling there is about two-three feet of open space between the drop ceiling and the actual ceiling. Also, the walls stop at the drop ceiling so once you get up in the ceiling you'll want to hide out on the wall section so it can support your weight. The zombies won't be able to get into the ceiling or be able to see you so you'll likely be undetectable. If the zombies have the standard zombie level intelligence they won't be able to construct anything that will allow them to climb up to you and if you're unlucky to have the smart zombies they won't look for you there as long as they don't see you climb up and you replace the ceiling tile.
Elevators are a gamble as both a place to hide and a way to escape; you don't know what will be waiting when the doors open. They might make a decent hiding place if you can keep it stopped and the doors closed (you have the key or whatever) it does have the advantage of having an emergency phone that could be useful. A truly daring option would be to hide on a window ledge. As long as you don't have to stand in front of a window you won't likely be seen. You should be safe enough on a wide ledge. But wind and ledge strength are unknown variables that could really change the outcome.
However you hide, hopefully, you'll be able to hold out until things settle down and you can make your escape.
I think that covers pretty much everything for an office attack. Suggestions, comments, concerns, please post.