It takes reframing the area in which the pocket door operates. Which usually means tearing out sheetrock, wall studs, moving any electrical wiring/switches, reframing the pocket door frame, installing the door, replacing the sheetrock, priming, painting, and installing the trim.

If you can do all those things----piece of cake.

They are a major framing task.

You can omit a large header in a partition wall, but a header twice the width of the door is needed in a weight bearing wall unless you have a wall thick enough to take both the door pocket and studs turned flat ('wet walls' with soil stacks often are thick enough for this trick, but then you need to avoid the stack).

I was going to install a pocket door before I discovered waste pipes running through the wall that would be a major deal to reposition. Instead, I 'built' a new wall attached to the existing studs and left the proper area for the pocket door, then drywalled to enclose. Yes, I have an extra thick wall but most do not notice and I now have beautiful double pocket French doors opening to my library.