A professional translation requires time to be done and finalised. Most people do not see the importance of the document being deeply checked by a second Translator, because of time and money manners. However, even the most experienced Translator may commit small mistakes. We must always remember we are not dealing with machines or computerised translation, but human beings. Proofreading in theory is a faster job than translating, but as important as. It is basically about reading the translated document all over again, as many times it is necessary, comparing it to the original and looking for typos, misspelling and grammar mistakes.
Knowing about this dislike of some companies about this process in translation and aware of the unreasonable charges some Translators might ask for this job, I always give a fair price for my proofreading. I proofread only from and into my mother tongue, which is Brazilian Portuguese, in order to maintain the high quality level of the translation. If you have doubts about proofreading prices, do not hesitate in contact me on firstname.lastname@example.org.