I second everyone’s advice to chat to your vet. Onsior and Pardale V are similar, and whilst I do commonly use a combination of an NSAID such as Onsior with paracetamol (in Pardale V) I will tend to ask for consent to use human paracetamol in place of Pardale V, particularly if paracetamol is to be taken every day or most days. This is because the dose rate of paracetamol with Pardale V is higher than that which you can dose effectively using human paracetamol. It is important to get veterinary advice and not use human paracetamol without this advice. As with NSAIDs it is also important to carry out regular (at least 6 monthly) blood tests to check organ function.
Mad Carly mentioned the two drugs work in different ways to control pain and certainly they can be used together to great affect. The idea of using more than one drug to control pain is that you can potentially get away with lower doses each drug so the risk of side effects is less. Always follow the doses your vet has advised.
As Bev has said it would be best to chat to your vet as they have prescribed the medication for your pet, sometimes meds can be used in combination with each other but as they have been treating them it is better to have a chat with them about different types of medication, as all of them work in slightly different ways and so there may have been a specific reason for prescribing one over another, they really wouldnt mind you having a chat with them about it I am sure
Prsumably your vet has prescribed them and given you instructions? I’d always follow their advice, if it wasn’t clear, call them, I’m sure they won’t mind.