It is always best to present original copies of your birth certificates and marraige as at one point they will probably ask for them so best to send originals I recommend all the time. Any other documents as diplomas can be copies as long as they are notorized or by a notary public that they are copies of the real documents.
Never send any Originals until & unless asked for, except for IELTS test result & PCC (Later when requested by VO). Just provide a Notarized copy of the documents.
But it is always better to check your Visa Office Specific Document along with the Instruction Guide.
rol17 said:
Do we need to submit the original birth and marriage certificates ,or the copies would be fine?It is not clear in the guide.