In order to extent your visa, you have to submit:

• an application for visa extension (Schengen visa , national visa )
• an up-to-date 4.5 x 3.5 photograph of the person looking straight ahead,permanently attached to the application by sticking it in a relevant place(the photograph should show the person without a headdress or glasses with dark lenses, with eyes open and not covered with hair, with a natural face expression and closed mouth and with her/his face being evenly illuminated; a person with a sight defect wearing glasses with dark lenses may attach photographs of her/him wearing glasses with dark lenses; a person wearing a headdress due to the requirements of her/his religion may attach the photographs of her/him wearing a headdress, but the headdress may not prevent the identification of the person)
• a travel document valid at least 3 months after the planned date of leaving the territory of the Republic of Poland containing at least 2 blank pages and issued within the last 10 years
• documents confirming the purpose and terms of visa extension 
• documents confirming that you have enough funds to cover the costs of your stay on the territory of the Republic of Poland and the return trip to the country of origin or residence (a foreigner entering the territory of the Republic of Poland for a period longer than 3 days should have funds of at least PLN 100 for each day of the planned stay or the equivalent of this amount in a foreign currency)
• documents confirming health insurance coverage as defined by regulations on health care benefits financed from the public funds or medical travel insurance for a minimum sum insured of EUR 30,000, valid for the period of the foreigner's planned stay on the territory of the Republic of Poland,
• a confirmation of stamp duty payment.

When submitting the photocopies of the required documents, you should present the originals.