I have a problem. I would like make a pdf, but I can not to make a simple flex and items-center on different height divs.
<div style="margin-top: 20px; align-items: center">
<div style="width: 70%; display: inline-block; text-align: right">Client: </div>
<div style="width: 25%; display: inline-block; font-size: x-large" >Company shorted name</div>
</div>
Okay, your problem is not really related to either Laravel nor DomPdf (Will adjust your tags :-)).
This is however how you get the 2 elements centered; The center is exactly between the 2 child DIVs, so you might want to adjust that with giving them a certain size, istead of auto.
<div style="margin-top: 20px; display: flex; justify-content: center;flex-direction: unset;width: 100%;align-items: center;">
<div style="flex: 1;display: inline-block;text-align: right;">Client: </div>
<div style="flex: 1;display: inline-block;font-size: x-large;">Company shorted name</div>
</div>
As reference you should have a look at this article https://love2dev.com/blog/absolute-centering-css/