In the Player's Handbook (PHB), the rules for taking the Dash action read:
When you take the Dash action, you gain extra movement for the current turn. The increase equals your speed, after applying any modifiers. —PHB, p. 192
The rules also provide a list of "the sorts of things you can do in tandem with your movement and action" (PHB, p. 190; Interacting with Objects Around You sidebar), including the ability to "draw or sheathe a sword".
Can a PC draw/sheathe a weapon during his/her movement AND draw/sheathe a weapon during a Dash action taken on the same turn?
Ranger fires longbow at enemy from a long distance.
Ranger stows longbow and begins to approach enemy.
Ranger draws scimitar with right hand while continuing to approach enemy.
Ranger uses the Dash action while drawing a second scimitar.
Rogue approaches enemy from a distance.
Rogue fires crossbow.
Rogue Dashes and stows crossbow. (A Rogue's Cunning Action feature [PHB, p. 96] enables them to Dash, Disengage, or Hide as a bonus action.)
Rogue draws shortsword while approaching enemy.
Rogue Dashes up to enemy while drawing a second shortsword.
Rogue attacks with shortswords.