Can anyone please explain what is the best decentralized storage protocol for storing pdf/images data on Polkadot parachain? Actually, I gone through filecoin, Crust and Cess. Now I'm little confused about this. Can anyone also have any idea what storage is widely used by most of the parachain? Thanks in advance
IPFS will likely be the best option for offchain + decentralized storage.
If you are willing, and able, you could run your own IPFS nodes to host your data in IPFS. However, if you would rather outsource your node operation, there are some services that provide this.
Crust Network is another good option. They host a deployment of polkadot.js.org on IPFS, and is used by a few NFT parachains, such as RMRK (see Crust's homepage for more). Crust will likely be cheaper than Pinata.