Can I add more RAM memory to my 2017 iMac?

Currently 27" iMacs have been discontinued, however you can find a few models on Apple's refurbished page or you can find used one's on www.macsales.com which is a reputable reseller. DO NOT buy a used Mac from a source like E-Bay, Craigslist, Marketplace etc... You don't know what you are really buying,

Link-> Install memory in an iMac - Apple Support

If its a 2017 21.5" iMac it is possible, but requires complete disassembly of the iMac. Apple suggests procuring the services of an Authorized Service provider to have them upgrade the ram for you.

On 27" iMacs the RAM is user upgradeable through the removable panel on the back of the iMac.

 iMac (21.5-inch, 2017), iMac (Retina 4K, 21.5-inch, 2017), and iMac (Retina 4K, 21.5-inch, 2019). If the memory in one of these computers needs repair service, contact an Apple Retail Store or Apple Authorized Service Provider. If you’d like to upgrade the memory in one of these models, an Apple Authorized Service Provider can help. Before you schedule an appointment, confirm that the specific Apple Authorized Service Provider offers memory upgrade services.

Is it a 21.5" or 27"?

• If 21.5" no you cannot add additional RAM.
• If 27" yes you can add additional RAM. Please either use Crucial.com or Macsales.com RAM. Both vendors provide very fair pricing, offer lifetime guarantees on their RAM and only sell high quality products.