So I have an A4 artboard files from my boss and a 1440px artboard from my work, he wants me to bring my artboard to that A4 artboard so I copy my artboard (which is 1440px in width) and paste to the A4 artboard and the problem is its too big to fit in that A4 artboard, I did search about the A4 size in px and had this info : A4 size in px with 300 PPI: 3508 x 2480 px but in the A4 file I have, it only has 841 x 595 px and now I'm struggling to make my artboard fit in it with precise size because I don't really want to scale my project because I'm affraid it will be too small on A4 or be rasterized and broke when print it out. (I'm not so good at English so please forgive me if my paragraph is wrong somewhere) Thanks in advance.
As I (mis)understand it and presuming vector artwork (or you may need to adjust raster effects or go back to vector artweork), I believe that yous (your boss and you) will be happiest if you (you can use either px/pt or mm as unit and just add the other unit when it is needed, and Smart Guides are your friends):
0) Work on a new document and keep the old one as backup;
1) Set your Artboard to A4;
2) With the rectangle Tool ClickDrag between opposite corners of the Artboard, this will be an A4 rectangle, set the Fill to None;
3) Change the W value to 1440px in the Transofrm panel, then hold Ctrl/Cmd and press Enter;
4) Move the 1440px rectangle to best fit round the artwork;
5) Select both rectangle and artwork and Change the W value to 210mm in the Transofrm panel, then hold Ctrl/Cmd and press Enter, then Group;
The 1440px rectangle is now an A4 rectangle with all the artwork best fit inside;
6) Deselect, then move the Group by the upper (or lower) left corner Anchor Point of the rectangle to snap to the A4 Artboard;
Now everything is resized and in place;
7) Ungroup and hide/delete the rectangle (which is now A4).