在iOS上，显然你必须通过UIDocumentInteractionController进行本地化。
你可以创建一个原生插件，比如

Assets/Plugins/iOS/iOSOpenURL.mm

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内容如下

#import <UIKit/UIKit.h>

@interface FileOpener : NSObject

- (void)openFileAtPath:(NSString *)path;

@end

@implementation FileOpener

- (id)init
{
    self = [super init];
    return self;
}

- (void)openFileAtPath:(NSString *)path {
    NSURL *fileURL = [NSURL fileURLWithPath:path];
    UIDocumentInteractionController *controller = [UIDocumentInteractionController interactionControllerWithURL:fileURL];
    controller.delegate = (id<UIDocumentInteractionControllerDelegate>)self;
    [controller presentPreviewAnimated:YES];
}

@end

// NOTE: parts below here are coming from the example under https://docs.unity3d.com/uploads/Examples/iPhoneNativeCodeSample.zip

static FileOpener* fileOpener = nil;

// Converts C style string to NSString
NSString* CreateNSString (const char* string)
{
    if (string)
        return [NSString stringWithUTF8String: string];
    else
        return [NSString stringWithUTF8String: ""];
}

// When native code plugin is implemented in .mm / .cpp file, then functions
// should be surrounded with extern "C" block to conform C function naming rules
extern "C" 
{
    void _OpenFile(const char* path)
    {
        if (fileOpener == nil)
            fileOpener = [FileOpener alloc];

        [fileOpener openFileAtPath: CreateNSString(path)];
    }
}

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它基本上将您的请求转发到上述UIDocumentInteractionController
然后在它旁边有相应的c#文件，例如

Assets/Plugins/iOS/iOSOpenURL.cs

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与此内容

using System.Runtime.InteropServices;

public static class iOSOpenURL
{
    [DllImport("__Internal")]
    private static extern void _OpenFile(string path);

    public static void OpenFile(string path)
    {
#if UNITY_IOS && !UNITY_EDITOR
        _OpenFile(path);
#else
        throw new OperationNotSupportedException("Only works on iOS!");
#endif
    }
}

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然后回到Unity编辑器中单击本机iOSOpenURL（它应该有一个插件图标），并在检查器中进一步配置它-因为使用相应的文件夹名称，它应该已经选择了iOS作为支持的目标平台-这意味着对于任何其他构建目标，此插件将不会包含在__Internal.dll中
参见See also Building plug-ins for iOS
最后，再加上你已经拥有的Unity-Android-Files-Opener，你基本上可以把它们组合成这样的东西。

public static class LocalFileUtility
{
    public static void OpenFile(string filePath)
    {
#if UNITY_ANDOIRD && !UNITY_EDITOR
        UnityAndroidOpenUrl.AndroidOpenUrl.OpenFile(filePath, "application/pdf");
#elif UNITY_IOS && !UNITY_EDITOR
        iOSOpenURL.OpenFile(filePath);
#else
        Application.OpenURL(filePath);
#endif
    }
}

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这是derHugo's answer的后续版本。
我试图实现derHugo的代码，但在执行过程中似乎遇到了一个错误：

UIDocumentInteractionController delegate must implement documentInteractionControllerViewControllerForPreview: to allow preview

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为了避免这种情况，应该在derHugo的代码中添加：
1/在界面中：

- (UIViewController *) documentInteractionControllerViewControllerForPreview: (UIDocumentInteractionController *) controller;

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2/在执行中

- (UIViewController *) documentInteractionControllerViewControllerForPreview: (UIDocumentInteractionController *) controller {
    return UnityGetGLViewController();

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