decrypting a pdf file [password available]

theres an android app which uses radaee and realm and decrypts a pdf file like this:

public final void NZV() {
     v3 = new n04(this.OJW.storagePath, this.OJW.getWrappedKeyBase64());
     Document v4 = new Document();
     int v3_1 = v4.OpenStream(v3, null);
     }

public String getWrappedKeyBase64() {
    return this.realmGet$wrappedKeyBase64();
    }

public n04(String arg2, String arg3) {
    this.NZV = new nd4(arg2, arg3);
    this.seek(0x7FFFFFFF);
    this.MRR = this.OJW;
    this.OJW = 0;
    this.seek(0);
}

public nd4(String arg2, String arg3) {
    jd4 v0 = new jd4(arg2, arg3);
    this.NZV = v0;
}

public jd4(String arg1, String arg2) {
    super(arg1, arg2);
    }

how can I decrypt this pdf on windows with the base64 key?