They at least knew of each other

While there is no recorded meeting of Aragorn and Saruman before the War of the Ring, Aragorn was a confidentconfidant of Gandalf and Elrond and would have at least have heard a lot about Saruman.

When Aragorn was young, he traveled in the south and served in Rohan and Gondor under the assumed name of Thorongil ("the Eagle of the Star"). At this stage he had heard enough to advise Ecthelion (the father of Denethor) to trust Gandalf rather than Saruman.

Thorongil often warned Ecthelion not to put trust in Saruman the White in Isengard, but to welcome rather Gandalf the Grey.

_{The Lord of the Rings Appendix A I (iv) Gondor and the Heirs of Anárion}

When Aragorn joins Gandalf, Théoden and others in the parley with Saruman after the Battle of Helm's Deep. Saruman recognises Gandalf and Théoden, but not Aragorn.

‘But come now,’ said the soft voice. ‘Two at least of you I know by name. Gandalf I know too well to have much hope that he seeks help or counsel here. But you, Théoden Lord of the Mark of Rohan, are declared by your noble devices, and still more by the fair countenance of the House of Eorl.

_{The Lord of the Rings Book Three, Chapter 10: The Voice of Saruman}

However, when Argaorn tells Gimli and Legolas what happened when he looked in the Palantír, he suggests that Saruman might have recognised him if he wasn't dressed like the Rohirrim.

To know that I lived and walked the earth was a blow to his heart, I deem; for he knew it not till now. The eyes in Orthanc did not see through the armour of Théoden; but Sauron has not forgotten Isildur and the sword of Elendil.

_{The Lord of the Rings Book Five, Chapter 2: The Passing of the Grey Company}

That quote is the closest I can find to evidence that Aragorn and Saruman had met, but it is clear that they knew a lot about each other.