Vishnu Purana Epic in Tamil is provided by Digital
Library of India – an undertaking of the Government of India. You can read and
download the Tamil Vishnu Puranam credited to T.C. Partha sarathi. You can read
the epic online and there is also an option to download but it works rarely.
Please note that it is not in pdf format.
Link – This is the link to the first chapter of Vishnu Purana Epic in Tamil. (You will need to download software to read the epic
from the website)