If you need a US state apostille for Spain, there are three main ways to get it: mail submission, in-person submission, and professional apostille services. Each method has its pros and cons depending on your timeline, location, and comfort with handling official documents.

This is the most common and least expensive choice. You collect your original documents (or certified copies), fill out the apostille request form that your state gives you, include the required fee (usually a check or money order), and mail everything to the Secretary of State's office.

If you don't have to do this urgently, this is a good choice. A lot of people use this method when they live far away from the state office or are submitting just one or two documents.

Mail submissions take 1–3 weeks for most states, though California SOS and New York DOS can run 3–6 weeks during peak periods. Texas SOS is usually faster, often under 10 business days. There is also a small but real chance that documents will be delayed or lost in the mail. So, it's a good idea to use a mailing service that can be tracked and keep copies of everything you send.

If you can go to the Secretary of State's office, this is usually the quickest and easiest way to complete apostilled US documents. Some US states let people walk in, while other states want to book an appointment.

The best thing about this is how quickly you can get your apostille. You can usually get it the same day or within 24 hours, but the actual time depends on SOS. In-person submission is also good if something is wrong (like missing notarization or the wrong type of document), as you can fix that right away.

The only drawback is that it's not convenient. You might have to wait in line and plan around limited business hours to get to the office. This option also might not work for people who don't live in the state or the office that issues it.

A professional service makes sense when you're handling more than two documents, working to a visa deadline, or submitting across multiple states at once. Apostille service providers are mediators. They check your U.S. documents for Spain and make sure everything is in order, and send them to the right state office for you.  

A lot of agencies offer tracking updates and can help with things like notarization or certified translations. This ease of use does, of course, come at a cost. The service fees depend on how urgent the request is and how many documents there are. However, many people find the reduced stress and quicker processing time valuable when errors could result in setbacks with visa applications, school enrollment, or legal procedures in a foreign country.