libpdfviewer/app/src/main/assets/viewer.css

body, canvas, #padding {
    padding: 0;
    margin: 0;
}

#padding {
    min-width: 100%;
    background: black;
}

.textLayer {
    position: absolute;
    text-align: initial;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    overflow: hidden;
    opacity: 0.2;
    line-height: 1;
}

.textLayer span,
.textLayer br {
    color: transparent;
    position: absolute;
    white-space: pre;
    cursor: text;
    transform-origin: 0% 0%;
}

.textLayer .highlight {
    margin: -1px;
    padding: 1px;
    background-color: rgba(180, 0, 170, 1);
    border-radius: 4px;
}

.textLayer .highlight.appended {
    position: initial;
}

.textLayer .highlight.begin {
    border-radius: 4px 0 0 4px;
}

.textLayer .highlight.end {
    border-radius: 0 4px 4px 0;
}

.textLayer .highlight.middle {
    border-radius: 0;
}

.textLayer .highlight.selected {
    background-color: rgba(0, 100, 0, 1);
}

.textLayer ::selection {
    background: rgba(0, 0, 255, 1);
}

.textLayer .endOfContent {
    display: block;
    position: absolute;
    left: 0;
    top: 100%;
    right: 0;
    bottom: 0;
    z-index: -1;
    cursor: default;
    user-select: none;
}

.textLayer .endOfContent.active {
    top: 0;
}