Are you trying to amend the soil, elevate the beds, or both? For soil amendment (adding 1" or so), you can spread compost around the crowns of plants and gently mix it into the top layer of soil. If you want to actually increase the height of the beds, you will have to lift the perennials and replant so that the crowns are at their original level. They will not be happy getting covered with soil.

Also, if your intention is primarily to improve the soil, it's a good idea to be sure that the topsoil you are using is actually fertile. There is no regulation of topsoil fertility -- it's just what's found on top in any given location. I've gotten 8+ yard deliveries of lovely stuff from old barnyards as well as detrius from what was probably a trash lot. (Guess which company I'll use in future!) Your best bet for regular soil improvement is compost -- some municipalities have this available in bulk or you can get it at a big box store in a bag (more expensive, but in some ways easier to spread).

Good luck -- and take care of your back!

Juliana

Good advice from Juliana63. Top soil seldom has any nutrients and sometimes is actually dyed black to make it look good. Get good quality triple mix from a reputable supplier. Are you able to make your own compost? That's
the very best thing for adding to your soil.

You can sprinkle used coffee grounds around for a boost. Starbucks has a program called 'Grounds for you garden' and they give the used grounds away free. Tim somebody's in Canada possibly gives theirs away as well. You just have to ask. You might get a few strange looks, but hey, you are reducing their waste costs, and doing a good thing for your garden.

And any mulch made from organic matter will eventually break down and add something to your soil. It's nature's way. My beds get landscape chippings, bunny poop, corn gluten meal (supposedly slightly pre-emergent herbicide qualities in that one,) and alfalfa pellets (rabbit feed, along with coffee grounds. (Go easy on the cofee grounds, corn gluten meal, and alfalfa pellets. I learned the hard way to do just a dusting of those three, then when they have 'disappeared' I can add more. Too much can get rank.) Not immediate results from any of it, but each year my soil looks better and better.