How to manage PDF files between laptops and iPAD?

If you'd like to manage(sync) files between different devices like laptops, iPAD, smart phones, there are several cloud service options available for you like Dropbox with 2GB free space and Onedrive from Microsoft with 10GB free and so forth. There's no difference among these solutions if you only want to use file synchronization function, and there's no doubt about that the larger space, the better the service is in this case. 

I'd like to show manage files between laptops and iPAD and including modifying files within the flow.

1.Dropbox

If you registered Dropbox and installed it in your computer, the icon will be shown in under your favorite automatically. You could save any files you want to save in the Dropbox cloud service and use it in another devices. The reason why I choose Dropbox over Onedrive is because PDF note (which is the iPAD app can manage PDF files efficiently) only support to sync with Dropbox and Google Drive.

2.PDF notes (iPAD application for managing PDF)

It is free to download and can manage PDF files importing from Dropbox, Google Drive and can mark sentences and modify PDF while reading. After you mark on whatever parts you'd like to, you could also save the modified file and upload the modified version to Dropbox. Then you could read the version from your desktop or laptop and other devices as well.