Download the trial version and install it, then use your serial number to "activate" it. Yes, the trial version is the full version. Your Lightroom 3 serial number will not work for Lightroom 5. If you want to install Lightroom 5 it will be necessary for you to purchase an upgrade. Then you will have to serial numbers to keep track of. Your original serial number plus the serial number for Lightroom 5. The links I have provided will enable you to download the right version for which you have a valid serial number.
Thank you. I have upgraded to LR5 on my home Mac, but I do not remember getting serial numbers when I upgraded. I guess i will have to call them Monday to obtain that. Thanks for your help!
If you registered your copies of Lightroom with Adobe, you can login to your Adobe account and get the serial numbers from there.You have to have received a serial number for Lightroom 5. Each major version requires as separate serial number.