When sharing documents internally from SharePoint, no emails are needed. You can simply send a link to the document. This is best practice because it ensures the recipient is receiving the latest version of the document and does not require any email attachments which can cause users to be looking at outdated documents.
Sending a link can be done in two ways. You can copy the link and send to the recipient via your chosen delivery method, such as IM, or send the link directly from SharePoint to the recipient via Outlook.
By default, the files in SharePoint are inheriting permissions from the library is which they are stored. This varies based on the library in which you are using. You do have the ability to change permissions on a file and allow access to users that do not currently have access using the share or you can simply send a link to someone that already has access to the document.