Dear Client,

This depends on facts of case in what manner position abused as ‘criminal misconduct’ is restricted to the following 2 offenses: (i) dishonest or fraudulent misappropriation or otherwise conversion of any property entrusted to a public servant or any property under his control as a public servant or allows any other person so to do; or (ii) if the public servant intentionally enriches himself illicitly during the period of his office.

Forging documents by IO dose not cover under PC Act but under Indian Penal Code and disciplinary action.

If there is no evidence of pecuniary benefit, however there is evidence of misuse of position, fabrication of docs to benefit someone.
Then in such a case can a public servant be charged under Prevention of Corruption Act?

Yes. Under Section 13(1)(d) of Prevention of Corruption Act.
In Union of India Vs. K.K.Dawan AIR 1993 SC 1478, the Hon'ble Supreme Court has mentioned the circumstances under which an inference can be drawn for initiating prosecution for the offences under Clause (iii) of Sec. 13(1)(d) of Prevention of Corruption Act 1988.
Mentioning only the relevant portion here ... "If he had acted in order to unduly favour a party; and If he had been actuated by a corrupt motive however small the bribe may be".

Let's say, if the officer has favoured his son by fabricating some certificate, then he cannot get away saying pecuniary benefit is not involved and hence cannot be charged under PC Act.

Pecuniary Advantage meaning:

Though every kind of gratification is not pecuniary advantage or valuable thing, pecuniary advantage and valuable thing are included in gratification (Bhawan Sahai Vs. State, AIR 1960 SC 487 Cr.L.J. 676).

Please rate the answer. It will help us to serve better.

1)he Supreme Court  has emphasised that proof of a demand for illegal gratification is the gravamen of offences under Sections 7 and 13 of the act and, in absence thereof, charges cannot be upheld.

i2)  in the case of Krishan Chander v State of Delhi the Supreme Court postulated on the essential factors for determining whether bribery, as contemplated under Section 7 read with Section 13 of the act, has been committed. The court held that in order to prove an offence under these sections, it is necessary to establish that the public servant both demanded and accepted the bribe.

3)  in the absence of any proof of a demand for illegal gratification, a public servant's use of corrupt or illegal means or abuse of his or her position to obtain any valuable object or pecuniary advantage cannot be proven.

See there are two aspect of this first if gratification other then pecuniary is received then same can corroborate to the offence as under section 13 Prevention of Corruption Act. 

Further if there is no proof of any gratification no demand or pecuniary benefit is proven then the offence under section 13 Prevention corruption cannot be proven, 

Further fabrication of documents is punishable offence under Indian Penal Code.

For benefit first establishing demand is necessary as judgement of Bombay high court in [Sukhdeo Lakshman Parale v. State of Maharashtra, 2018 SCC OnLine Bom 1194, held.

Making ‘demand’ of bribe is essential to establish the culpability of a person accused of taking illegal gratification under Prevention of Corruption Act, 1988.

The case can be filed even if there's pecuniary benefits but there is an evidence for his involvement in the act of crime.

About fabricated case or wrong implication in the case, it can be argued before court.