A document is meant to be kept and sent. A scan is not the same as a page of real text. A signature and a second copy make it easier to recover after a mistake.
A document is a file kept so it can be read, stored, and sent.
A document is a file kept so a task or a piece of information can be read later.
A letter, a form, a contract page, and a scanned sheet are documents in this sense.
A photo album or a music file is usually not kept for that job.
A scan starts as a picture.
If you can select the writing, the document has real text.
A scan is a page taken by a camera or a scanner.
At first it is a picture.
The letters are visible, but a program may not know them as writing.
Text recognition tries to pull writing out of that picture.
A signature shows that you accept this copy.
Read the page before you sign.
A signature is a mark that you accept this copy of the document.
On paper it is drawn with a pen.
On a phone it can be drawn with a finger or a stylus.
When the signature image is added, keep that copy separately.
A second copy of a sent or changed document is the way back after a mistake.
Merging, reducing, or sending a document can change the original.
A second copy is the file kept before that action.
If the action goes wrong, you can return to that copy.
