I want to change Order ID number series, rather than typical Magento Default #000000001.
please Tell me how could i change this and also change the Pdf Invoice number.
Well AKAIK - by default (native) there is no functionality/option to change Order ID.
Series will remain same and it is auto incremented !
But yes there is one extension available of Amasty . which does the same functionality which you have mention.
Refer this link for the same- https://amasty.com/custom-order-number-for-magento-2.html
Hope it helps !