Yes, you must download and install the original 071102 Upgrade before you are able to install any service packs.
If you have the Upgrade email for the 071102 Ledger 9.0A upgrade, the link on the email will allow downloading. You need this email along with new serial number and installaton codes. Once that is done, you can install the latest service pack - you do not have to install any of the 'in-between' service packs.
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Regards,
Softrak Tech Support