Not hard at all.
Install Xmarks extension in your Chrome browser on PC, create an account and sync your current bookmarks with Xmarks server.
On the Mac side, do the same. This time when you install Xmarks extension in Mac, just use the same account info you created earlier to sync the bookmarks.
I like Xmarks because it can work with any browser. I keep all my bookmarks synced between FF, Chrome, and Safari.