"Macron (equals) Louis XVI, Le Pen (equals) Le Pen", read another.
Le Pen says large companies that operate internationally would be allowed to continue using the euro, while ordinary citizens would use a new franc.
Le Pen, who hopes to mimic President Donald Trump's populist electoral victory, compared Macron to Hillary Clinton.
Mr Macron said, despite Marine Le Pen's efforts to distance herself from her father's anti-Semitism, "the roots are there, and they are very much alive".
"Since December French people thought they had gotten rid of Francois Hollande, that President so hated by the French people, that president who failed France, that president who never presided for the people".
In a speech before a gilded Paris statue of his heroine, Joan of Arc, Jean-Marie Le Pen urged French voters to back his daughter in the runoff.
But while three other more left-wing unions including the biggest, the CGT, have called for demonstrations against Le Pen's vision of French identity, they have stopped short of backing Macron whose economically liberal outlook worries many members.
"She grew up in the system, she inherited a party", Macron said on France 2 television late Sunday.
She launched a full-throttled attack on Mr Macron, calling him the candidate of "a morbid continuity, littered with the corpses of jobs transferred offshore, the ruins of bust businesses, and the gaping holes of deficit and debt".
But Ms Le Pen knows Mr Macron's time as economy minister in Francois Hollande's socialist government helps feed the narrative that he is the current President's lapdog.
Standing on the bridge, Macron hugged Bourram's son Said, who was 9 when his father was killed. But at the 1995 event, some skinheads broke away and pushed 29-year-old Brahim Bourram off a bridge into the Seine River, where he drowned.
Said, now a chauffeur who supports Macron, said his father was targeted "because he was a foreigner, an Arab".
Then, earlier this month, Le Pen sparked outrage by suggesting France was not responsible for the wartime round-up of Jews who were sent to Nazi death camps. "That is why I am fighting, to say "No" to racism".
Macron is seeking to remind voters of the dark past of rival Marine Le Pen's National Front party, which she has tried to detoxify.
In Paris's Place de la Republique, 28-year-old teacher Camille Delaye held a placard that read: "Abstention is a political act" - meaning he is so disgusted by both candidates, he will not vote on Sunday.
CGT leader Philippe Martinez said he "deeply disagreed" with that approach, arguing that Le Pen and Macron "are not the same thing". Macron joined the man's son and anti-National Front protesters at an annual commemoration near the Louvre Museum.
Le Pen took her campaign Monday to the working-class Paris suburb of Villepinte where the first speaker was Nicolas Dupont-Aignan, a eurosceptic from outside the FN who Le Pen has said will be her prime minister if she wins on Sunday.
On this day 15 years ago, some 1.3 million people, including 400,000 in Paris, took to the streets of France in union-led demonstrations to protest against the founder of the National Front (FN). Some groups want a united front to keep Le Pen from the presidency, but unions fear Macron will dismantle worker protections.