Can This Transformer be Used as a Step Up Transformer?

Yes. The rating 33/6.6 KV doesn't indicate it is step down transformer, it only indicates its HV rating is 33 KV and LV side is 6.6 KV. A transformer itself is not designated as step-up or step-down unless it is used for these purposes. If the transformer's other ratings including the vector group serve the requirement, it is perfectly ok to use.

- MS

As Msamad said we can use any transformer for step-down or step-up unless the vector group, frequency and voltage matches, we have to also take care of the Tap changers in the transformer. it also plays a significant role to use.

A transformer is a bi-directional device and your 33/6.6kV Step Down Transformer can very well be used as a 6.6/33kV Step Up transformer. But, there could be magnetising in-rush current problems while you charge the trafo from LV Side. Please underake a study of this. Also, take care about Vector Group, Earthing of Neutral, etc.

what about onload tapchanger which gets signal from secondary voltage and adjust taps by AVR to maintain a constant secondary voltage within limits?.