The short answer is yes, you can. This would be called a backup offer. However, it may not be worth your time, unless you’re very invested in the property. To understand why, let’s take a look at what a pending sale actually means, and what making an offer on a pending sale looks like.
When a property has the “sale pending” status, what it means is that the seller has accepted an offer, but the sale hasn’t yet been finalized. There are potentially several steps before a sale can be finalized, which can include contingencies, inspections, appraisals, and negotiations. Inspections and appraisals always take time, but may not be required. Not all sales have contingencies, but they come in multiple forms, some of which could take a long time — such as waiting for the sale of another property to close.
So while you could submit an offer on a pending property, not even the seller can know whether they will be able to accept it for a potentially extended period of time. If the pending sale falls through, they may accept or reject it, or want to negotiate further. Even if all of that works out, the property will then be pending with your offer. If you’re on any sort of time constraint, it’s probably not worth it. Furthermore, most pending sales don’t fall through, and half the potential reasons it could may reveal major issues with the property that might result in you not wanting it anymore.