Using QLPreviewController and SwiftUI to preview many common file types (PDF, iWork, Microsoft Office documents, images, texts, etc).

PreviewController+LocalFile.swift

import SwiftUI

struct DocView: View {
    @State private var buttonPressed: Bool = false

    var body: some View {
        Button {
            buttonPressed = true
        } label: {
            Text("Show PDF file")
        }
        .sheet(isPresented: $buttonPressed) {
            let localURL = Bundle.main.url(forResource: "Sample", withExtension: "pdf")!
            PreviewController(url: localURL)
        }
    }
}

PreviewController+RemoteFile.swift

import SwiftUI

struct DocView: View {
    private let urlSession = URLSession.shared

    @State private var isLoading: Bool = false
    @State private var localDocURL: URL?

    var body: some View {
        ZStack {
            if isLoading {
                ProgressView()
            } else {
                Button {
                    if let url = URL(string: "https://www.africau.edu/images/default/sample.pdf") {
                        loadDocument(with: url)
                    }
                } label: {
                    Text("Load and Show PDF file")
                }
            }
        }
        .sheet(item: $localDocURL) { url in
            if let url = url {
                PreviewController(url: url)
            }
        }
    }

    // MARK: -
    func loadDocument(with url: URL) {
        isLoading = true
        urlSession.downloadTask(with: url) { location, response, error in
            if let location = location {
                self.localDocURL = copyDocumentToCache(location, url: url)
            } else if let error = error {
                print("Error to download file: \(error)")
            } else {
                print("Unknown error")
            }
            self.isLoading = false
        }
        .resume()
    }

    private func copyDocumentToCache(_ locationURL: URL, url: URL) -> URL? {
        let documentsPath = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask)[0]
        let destinationURL = documentsPath.appendingPathComponent(url.lastPathComponent)
        try? FileManager.default.removeItem(at: destinationURL)
        do {
            try FileManager.default.copyItem(at: locationURL, to: destinationURL)
            return destinationURL
        } catch let error {
            print("Error to copy file to cache: \(error)")
            return nil
        }
    }
}

private extension URL: Identifiable {
    public var id: URL { self }
}

PreviewController.swift

import QuickLook
import SwiftUI

struct PreviewController: UIViewControllerRepresentable {
    @Environment(\.dismiss) private var dismiss

    let url: URL

    func makeUIViewController(context: Context) -> UINavigationController {
        let controller = QLPreviewController()
        controller.dataSource = context.coordinator
        controller.navigationItem.leftBarButtonItem = UIBarButtonItem(
            barButtonSystemItem: .done, target: context.coordinator,
            action: #selector(context.coordinator.dismiss)
        )

        let navigationController = UINavigationController(rootViewController: controller)
        return navigationController
    }

    func updateUIViewController(_ uiViewController: UINavigationController, context: Context) {}

    func makeCoordinator() -> Coordinator {
        return Coordinator(parent: self)
    }

    class Coordinator: QLPreviewControllerDataSource {
        let parent: PreviewController

        init(parent: PreviewController) {
            self.parent = parent
        }

        func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
            return 1
        }

        func previewController(
            _ controller: QLPreviewController,
            previewItemAt index: Int
        ) -> QLPreviewItem {
            return parent.url as NSURL
        }

        @objc func dismiss() {
            parent.dismiss()
        }
    }
}