just was viewing these features list on the site : https://info.magento.com/rs/magentocommerce/images/Magento%20Full%20Features%20List%20052714.pdf
want to know are all these features available in open source edition also ??
Also can we add multiple marchants/sellers to one site and make marketplace ??
Yes, you found the correct link which includes all the features of open source Magento ecommerce platform.
Magento has 2 editions 1. Community edition (open source) 2. Enterprise edition (Paid)
From the pdf, 1 to 6 pages contains the features of community edition and then there is a list of enterprise edition features.
Community edition doesn't include Marketplace functionality by default but yes we can help you with your requirements. You can contact us and we will be happy to help you out.
are there any free/paid plugin/addons for setting up marketplace on magento
Yes you can choose http://marketplace.webkul.com/add-ons/magento/ marketplace module and addons here