I tried looking at the link that Andrew Z posted, and found it confusing as some of the menu items you need to choose are different. To be clear, these are the steps:
- Go to Settings
- Select Application Saved Data Management
- Select Saved Data in System Storage
- Select Copy to USB Storage Device
- Find the world you want to Transfer and make sure you copy over the World Data (All of them if there is more than one) and the world itself as the world data will contain all the block data in the world after it's creation.
Now, as stated by ProBrownie on reddit: "Now you can upload the saved data to the internet and share with others, if you want to download maps open your memory stick and look in the PS4 folder which will automatically be made when you insert your USB Device into your PS4 System and copy it into the SAVEDATA folder. Once you have done enter your USB Device back into your PS4 and go to Settings, System Storage, Application Save Data, USB, Copy to System Storage then Select the files you want to transfer and you are ready to play the map you've just downloaded."