This is the 5080th most frequent Polish word.
prezydenckich
"Prezydenckich" means "presidential" (pertaining to the president).
The word 'prezydenckich' is used here as an adjective describing the type of elections—presidential elections.
Wyniki prezydenckich wyborów będą ogłoszone jutro.
The results of the presidential elections will be announced tomorrow.
Here, 'prezydenckich' characterizes the meetings taking place in the palace as presidential in nature.
Pałac prezydenckich spotkań znajduje się w centrum miasta.
The palace of presidential meetings is located in the city center.
In this sentence, 'prezydenckich' specifies the type of documents—those associated with the president.