for whom

This document is important not only for him, but also for his customers for whom such a document is the confirmation
that his company XXX sells your original spare parts.

Are there any other ways to say "for whom"?
If you have any other ideas how to rephrase this sentence, let me know, please.

Thank you.

I'm not a native speaker, just trying:

This document is important not only for him but also for his customers as it is the confirmation document that his…

The document is important not only for him, but also for his customers, as it serves as an assurance that his company, XXX, sells original spare parts.

This document is important for him and his customers because it confirms that his company, XXX, sells your original spare parts.

This document is important not only for him, but also for customers to which such a document is confirmation
that his company XXX sells original spare parts.

Skrej said:

customers to which

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Can 'which' refer to people?

Yes. 'Who', 'which', and 'that' can all be used to refer to people.

The above suggestions are OK, Ksenia, but inferior to the original sentence, in my opinion.

Why did you want to rephrase it?

Rover_KE said:

The above suggestions are OK, Ksenia, but inferior to the original sentence, in my opinion.

Why did you want to rephrase it?

Click to expand...

Because I thought that it was wrong...

Ksenia said:

Because I thought that it was wrong.

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Why did you think that?

emsr2d2 said:

Why did you think that?

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In Russisn we often say "for whom", but I thought it is not the same case in English.
I am not sure of myself.

In English 'whom' is rarely used. That's what I learned from this forum.