Hi, mahaveer!
When you install Dropbox in your PC it builds a folder structure as follows:
<Path>DropBoxApps
<Path>DropBoxDownloads
<Path>DropBoxPhotos
<Path>DropBoxPublic
<Path>DropBoxStart.pdf
A simple and initial use would be as follows:
a) copy the file you want to share from its original location to Public DropBox folder
b) right button on the copied file, DropBox, Get Public Link
c) paste the link and send it to the destinatary
As b(ut)ob(ut)hc said, always copy the file and don't expose your original keeping it only or moving to Dropbox.
Giving a look to the Start.pdf file wouldn't cause any harm
Regards!