Adventurers make a profession of taking jobs that others do not want or are unable to do. They do not have a social definition, yet the core rules state that adventurers do not stir any extraordinary attention by virtue of being adventurers. There are a few ways to resolve the magical medieval mindset and the social reaction to adventurers listed in the core rules. The best way of understanding adventurers from this standpoint is calling them mercenaries. They travel and act as sell swords and solve problems for wealthy people. Some also do some pro bono work, saving the occasional village from orcs or rescuing the farmer's daughter from the goblin's lair. Some wreak terrible damage for personal gain, slaying and pillaging as they go. Like mercenaries, PCs are heroes in armed conflict, but worrisome when the conflict ends. They are a dangerous lot by virtue of their mobility, their paucity of social sponsorship, and de facto, the lack of social restraint.
More than likely, then, is that PC adventurers draw at least some attention. First, most PCs usually wear armor and are fully equipped for combat and adventuring. This is not very common in a city, unless it is a time of war or a fort city where most people do soldiering. Even then, having a person in full armor with multiple weapons who is not an aristocrat or a knight is rather rare. Anyone showing up at a city's gates in full armor and fully armed, and who wishes to enter the city in such a state, has a lot of explaining to do. Unless they have a writ or badge identifying their social sponsor, most PCs probably have to surrender martial weaponry and all but light armor into the custody of the city until they depart, at which time, they can collect their things. Second, PCs have backpacks stuffed with interesting things that jingle. As they try to enter the gates, such loot attracts the attention of sellers, pickpockets, and the guards collecting taxes at the gate. On top of paying an entry tax, PCs pay for the goods they bring into the city, even if PCs claim they are not selling anything in town. Bribery, intimidation, bluff, diplomacy, and magic are always options for bypassing the gates and taxes, but PCs must remember that they are subject to the city laws and the force behind them. Third, should someone have the power to look (in larger cities gate guards are always equipped with detect magic) PCs have lots of magic. Cities tax PCs for the magic items they have, and the PCs should obey the civic rules on holding and using magic in the city. Some cities have strong groups that regulate the use and abundance of magic in the city. Some cities require people to surrender certain types of magic items and restrain the use of certain schools of magic in the city. PCs would do well to always get the specifics when entering a new city.
Large trade cities through which many people travel through are more acclimated to adventurers, mercenaries, and the shady lot of society. But for the most part, adventurers stick out in society. Retired adventurers are understandable, seen as wanderers who settled down and entered society at that point. Even if they adventure again, the retired adventurer has roots and social connections that tie him to a locale.
There is an undercurrent among the urban powerful to invite wandering PC adventurers into social obligations, and in effect, a social classification. Adventurers that accept such invitations become agents of a certain lord, religion, or ideal. Such relationships are also beneficial for PCs. Social connections are very useful, if only in tax savings alone. PCs who establish such ties have home bases, relinquishing rented beds and tourist prices for dinner invitations, choice gossip, and surety should something strange happen in their presence.
Another truism of the magical medieval city is that news travels fast, especially bad news, and it seems like everyone knows everyone else's business. When PCs roll into town, it doesn't take long for everyone to hear about them, know what they look like, and learn how many pitchers of ale they had at lunch. This can make subtlety and covert operations difficult for outsiders. People also know that PCs have lots of money, as displayed by the 50 pounds of metal the fighter wears, the goods they carry into the city, and the amount of magic on their person. This affects the prices they pay for goods and services, the number of touts and beggars that follow them around, and thievery attempts. If the PCs look rough and seasoned or if they come with a social connection, it is possible that no one in town wants that much trouble.