Paste this css in the customized css section of twenty seventeen:
.single-post:not(.has-sidebar) #primary, .page.page-one-column:not(.twentyseventeen-front-page) #primary, .archive.page-one-column:not(.has-sidebar) .page-header, .archive.page-one-column:not(.has-sidebar) #primary {
max-width: 1000px;
}
.page-one-column .panel-content .wrap {
max-width: 1000px;
}
@media screen and (min-width: 48em) {
.blog:not(.has-sidebar) #primary article,
.archive:not(.page-one-column):not(.has-sidebar) #primary article,
.search:not(.has-sidebar) #primary article,
.navigation.pagination,
body.blog .site-content .page-header,
body.archive .site-content .page-header,
body.search .site-content .page-header {
float: none;
margin-left: auto;
margin-right: auto;
max-width: 1000px;
width: auto;
}
}
References:
[ Sheriziya's solution works: ]