What is the exact version library for pdf view in android studio 3.1.3? implementation 'com.android.support:appcompat-v7:28.0.0-beta01'

Question

When I put a library for pdf view in dependencies in android studio 3.1.3 ,It shows the error message "All com.android.support libraries must use the exact same version specification ".What is the way to read pdf in this situation?

build.gradle file has the following code: apply plugin: 'com.android.application'

android {
compileSdkVersion 28
defaultConfig {
    applicationId "com.example.lenovo.myapplication"
    minSdkVersion 15
    targetSdkVersion 28
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0-beta01'
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.github.barteksc:android-pdf-viewer:3.1.0-beta.1'
}