[docs] new selling pages added

docs/user/buying/docs.user.buying.purchase_order.md

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 A Purchase Order is analogous to a Sales Order. It is usually a binding contract with your Supplier that you promise to buy a set of Items under the given conditions.
 
-In ERPNext, you can make a Purchase Order by going to:
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+A Purchase Order can  be automatically created from a Material Request or Supplier Quotation.
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+![Purchase Order](img/purchase-order-f.jpg)
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+In ERPNext, you can also make a Purchase Order directly by going to:
 
 > Buying > Purchase Order > New Purchase Order
 
-A Purchase Order can also be automatically created from a Purchase Request or  Supplier Quotation.
 
 
 ![Purchase Order](img/purchase-order.png)