As a rule, the registration fee for attending an ISHS symposium includes one hardcopy of the Acta Horticulturae proceedings mailed to the contact address you indicated when registering for the meeting.
Check with the symposium convener for possible exceptions to this rule such as e.g. single-day registrations or student registrations at reduced cost which may not always include a hardcopy of the proceedings.
ISHS does not provide authors with an electronic copies of the published Acta Horticulturae paper. ISHS membership comes with free article downloads; for those who do not have an active ISHS membership but still want to download articles, each Acta Horticulturae article is readily available for download on a pay-per-view basis instead. Authors who consider sharing their article; make sure to check out this FAQ item.