You are suposed to work at scale 1/1 and only when printing you "scale" the print ( but not the file ) with the dialog box of your printer ( but it's an other subject).

If you want to scale them to the right size you must verify in what unit they were drawn.

Type UNITS and take a look if there is an "insertion scale unit" and what it is.

If you set your drawing with the unit that you use ( inches , feet , millimeters , meters , etc ... ) then an insertion ( and not a copy/paste ) will bring the file ( that will become a block inside your file ) to the right scale.

If you use blocks of unknown persons then do a good check before using them.

Ask for more and have a good day. 

 

Take a look at this :

http://www.cadtutor.net/tutorials/autocad/units-and-scales.php" rel="nofollow - http://www.cadtutor.net/tutorials/autocad/units-and-scales.php

le problem que tu pose est un problem rĂ©curent pour les dĂ©butants dans autocad, il faux ce dire que tout dessin est fait a une Ă©chelle exacte. dans les version françaises d'autocad en majoritĂ© tu aura m cm mm qui sont des unitĂ©s rĂ©gulièrement utilisĂ©es dont verifit juste avec quel unite ((j'insiste sur le mot unite)) ton dessin de basse est et l’unitĂ© du  block que tu souhaite insĂ©rer la tu pourra choisir la quelle des unitĂ©s tu souhaite conservĂ©es. 

.........bonne comprenssion mon grand .......