When you sign a case your personal data is being saved. It will become available for the one who issued the case and shown on the receipt page of the e-signed document. This means that other parties to an agreement you sign can see your personal data.
For all Swedish eID's the Personal Identity Number is included in the e-signature. If you have protected personal details, please contact the issuer of your eID to see what personal information is being used when you e-sign.