Can you? In the sense that it's physically possible, sure. But I suspect you're really asking, "Is it advisable to do it that way?" What the professionals might say is up to them...but I'd much prefer NOT to install metal roof panels on an existing metal roof.
1. Unless the new roof has a pattern of raised ribs EXACTLY like the old roof, the ribs won't match up. The new layer won't be able to "lie down flat" on top of the old layer. It will be frustrating to install, unattractive, awkward, and easy for the wind to remove by force.
2. Even if the panels ARE exactly the same model as the old, there is still the matter of hundreds or even thousands of screw heads sticking up above the old panels to cause the same problems. A difference in degree, but still a major problem.
3. If the old metal does need replacement, it's not a bad idea to get it completely off the roof anyway--so that the underlying roof structure can be inspected for damage. Yes, it does mean the roofing felt will also have to be replaced, but if a problem with a section of sheathing board does exist, it's best to know about it.