It can happen that you apply different rates for a single service for a client, depending for example on the domain of expertise concerned. For example, you can decide to apply a higher rate than your "generic" rate for an FR-EN translation if it's a medical/legal or technical text.
In this case, you simply have to create different services that you can call "FR-EN translation - Medical" or "FR-EN translation Legal" for example, and define the corresponding rate for these services. When creating a job, you then simply have to choose the right service.
Note that the name of the service as you defined it will, of course, appear on the invoice. If you don't want to see "FR-EN translation - Medical" on your invoice, but simply "FR-EN translation" (because your client doesn't have to know your "internal business" with your rates), you can do as follows:
Under Settings > Document and email configuration, select the document configuration concerned.
Go in the "Master data" tab of this configuration. This tab is normally meant to "translate" your master data, but we will use it here to define a new "name" for your service, to be used in your documents.
Next to "FR-EN translation - Medical", simply write "FR-EN translation". This means that each time you select "FR-EN translation - Medical" in LSP.expert, you will see "FR-EN translation" on your PDF documents. What you see in the interface is thus different than what your clients will see on the document you will send them. You have all the details you need in the interface (i.e. the "medical" part to make sure you select the right service and the right rate) and you decide what the client sees on the document.
And of course, don't forget to go in the client's details and make sure you selected the right document configuration.