It's a free pdf editor and it's connected to your google drive account so it's easy and fast to edit your pdf files. Also. It's perfect to sign your pdf documents without to use additional software. You can download directly from it so you don't need to go to Google Drive to do it.
If you can share your edited pdf, you can do it, just click on the share icon and Lumin will send an email to your friend.
Sometimes Lumin can't recognize properly the pdf document and you can't edit a particular line of the document.
Also, I miss a feature to merge some pdf files.