My line weights are inconsistent at different resolutions

[sugarcoated293]

Hi,

I just wanted to ask whether I've done something wrong with my file. I have couple of boxes that I have copied and pasted so should have the same line weight. I converted my file to PDF

at 100%, the line is darker at the bottom.  

At  75%, the same boxes have different line width: 

And at another resolution, it's different again. 

I've printed this sheet and there doesn't seem to be any issues with the line weight. However, I also have encountered the opposite scenario where it looked okay on screen but when printed out, the line weights were different. I do use PDF to check that everything is okay and this seems like an unreliable way to do it. 

Is it something that I have done wrong?

[Doug A Roberts]

Are you viewing this file in Acrobat? Is Enhance Thin Lines checked in the preferences?

[sugarcoated293]

I'm viewing it in Adobe Reader. Yes the enhanced thin lines is checked. If it isn't checked, will it affect printing?

[Doug A Roberts]

No, it's a purely on-screen effect.

[sugarcoated293]

I see so best bet is to print and check. 

And maybe something is wrong with my monitor if the boxes are copies of each other but I'm getting different results.