Not necessarily. There are, arguably, several nations with a federal system that do not have representative democracy, at least not in any meaningful way, with elections that are neither free nor fair and leadership that is often authoritarian.
That could be said of representative democracy or democracy in general.
Democracy might not guarantee freedom in and of itself, and maintaining a free society requires that the people are vigilant, that they hold their government accountable (through both the ballot box and through speech and protest), hold their elected officials to high standards, demand transparency, and call foul when people's rights are trampled upon. But a hallmark of a free society is free and fair elections for the peoples' representatives in government. We have never seen a truly free society where the right of all citizens to vote was not respected. In other words, democracy may not guarantee freedom, but it is a prerequisite for freedom.
Meanwhile, "federal" is simply a term describing the relationship between a nation's central government and its sub-national units. It says nothing about whether the right to vote, or any other freedom for that matter, is respected. It merely says that the states/provinces share power with the central government and have a wide degree of autonomy that, at least in principle, cannot be unilaterally rescinded by the central government. This is opposed to a unitary state where the sub-national units only have whatever powers and autonomy, if any, the central government chooses to delegate to them. Typically, federations are either very large in terms of area (e.g., Canada, Australia, Brazil, India, Russia), or were formed when multiple independent entities unified into a single larger nation-state (e.g., Germany, Switzerland, Malaysia), or both in the case of the U.S.
Essentially, federalism almost always seems to be a practical consideration for a nation that's geographically large, or was a consequence of the nation's formation and/or other events in its history. There is nothing about federalism in and of itself that makes it a system desirable for a free, democratic nation. It's neither good nor bad.