FAQ

Issue overview

When saving some PDFs with embedded OCR text for search purposes, the text could become corrupted. This issue appears to be caused by the iOS PDF framework (for app developers) altering the embedded text data upon saving.

This issue has seemingly existed for some time, but for Booklover, it became apparent with the introduction of the annotating (highlighting) feature in version 3.3, which involves saving PDFs. We have confirmed that the same issue occurs when using the aforementioned PDF framework in a separate test app.

Since Booklover relies on this developer framework for saving PDFs, it is difficult for us to resolve the issue unless some fixes are made on the framework side.

Findings from current investigations

Corruption of OCR text

• There are PDFs where the embedded OCR text gets corrupted when saved.
• The OS PDF framework seems to alter the embedded OCR text data upon saving.
• After making changes (such as annotations in Booklover) in PDFs and saving, the OCR text becomes unselectable or incorrectly selectable upon reopening.

Only Non-Latin text seems to be affected

• It is some embedded Japanese or Non-Latin OCR text which gets corrupted (possibly related to font processing).
• English and other Latin texts do not seem to be affected by the issue.

Recent ScanSnap PDFs do not seem to be affected

• Non-Latin OCR text embedded by Adobe Acrobat is prone to corruption when saved (as of January 2025).
• PDFs with OCR text created by ScanSnap do not seem to have this issue (tested with the latest ScanSnap software).

Workarounds for corrupted PDFs

If you have a backup

If the OCR text becomes unselectable, please overwrite and replace it with the backup file. For the problematic PDFs, use the OCR text data only for search purposes and avoid adding annotations (such as highlights) in Booklover.

If You do not have a backup

You could use the "Recognize text" feature in the Adobe Acrobat Reader app for iOS to re-embed the OCR text data. Use a subscription or free trial period for this feature.

Adobe Acrobat Reader (App Store)

Recovery steps

1. In the Booklover library, long-press the PDF with the corrupted OCR text and tap "Share".
2. Select "Save to Files" and save it to the "Acrobat" folder under "On My iPhone (iPad)".
3. Open the Adobe Acrobat Reader app, select "On My iPhone (iPad)" from the side menu, and open the saved PDF.
4. Tap "All Tools" in the navigation menu.
5. Select "Recognize text" from the displayed menu and wait for the process to complete.
6. Open Booklover and tap the "Import" button at the bottom left of the library screen.
7. Select the repaired PDF from the "Acrobat" folder under "On My iPhone (iPad)" and tap "Open".
8. A dialog will appear if a file with the same name exists. Select "Replace" to overwrite with the repaired file.

Notes

Adding annotations to PDFs with OCR text embedded using Adobe Acrobat may cause the text to get corrupted again upon saving in Booklover. Therefore, use the OCR text data only for search purposes and avoid adding annotations to such PDFs.

As of the end of 2024, the following issue have been observed when importing from Google Drive:

1. Regardless of the file extension, particularly with large files, downloads and imports are unstable.
2. If an import fails, the files become "stuck" and do not complete, even after a long time. The state of these files does not seem to reset until the device is restarted.

Currently, these issues have only been observed with the Drive (Google Drive) app. They have not been observed with the OneDrive or Dropbox apps, which Booklover also accesses through the same iOS File Provider Extension.

We suspect this might be a temporary issue with Google Drive or with the interaction between the Drive app and iOS. We will continue to monitor the situation to see if it resolves over time.

After upgrading to iOS 18 and iPadOS 18, it seems that even if you clear the content cache of books stored in iCloud Drive/Booklover from your library, they may be automatically re-downloaded aggressively, regardless of file size. (Even though the cloud label on the top right of the book turns blue after clearing, it reverts to green after a while.)

This seems to be an issue in iOS 18, and the exact reason or cause is still unclear at this point. However, we have found a potential workaround to prevent this.

1. Open the "Files" app from the home screen of your device.
2. In the sidebar, select "iCloud Drive" under "Locations" and open the "Booklover" folder from the list on the right.
3. Tap "Select" and then "Select All" to choose all files and folders in the folder.
4. From the "More…" menu at the bottom right of the screen, choose "Remove Download."

After following these steps, the unwanted re-downloads no longer seem to occur. (However, the auto-downloading of lightweight files, which has been occurring since iOS 17 or earlier, may still happen.)

We will attempt a fix as soon as we determine if any action can be taken on the developer side regarding this issue.

If the 'Booklover' folder is not automatically created when checked in 'Files' app, please try the following steps.

1. Turn off 'Sync this iPhone' in the device's 'Settings' under iCloud Drive settings. (For iPad, it will be 'Sync this iPad'). Restart the device and turn it back on.
2. Select an appropriate book in Library using the 'Select' option at the top right of the screen.
3. Tap the icon at the bottom right of the screen that looks like 'an arrow coming out of a box' (which means 'Share').
4. Execute 'Move to iCloud Drive'.
5. The book will be moved to iCloud Drive, and the 'Booklover' folder will be created in iCloud Drive simultaneously.
6. From then on, files within the 'Booklover' folder will be synchronized.

(Books moved to iCloud Drive can be selected again in the library and returned by choosing 'Move to Local'.)

Please do NOT manually create a folder named 'Booklover' in iCloud Drive. When you first launch Booklover, a folder with the app's icon and named 'Booklover' is automatically created in iCloud Drive. You can confirm the existence of the 'Booklover' folder with the app's icon in the standard 'Files' app within iCloud Drive.

Book files in the Booklover folder on iCloud Drive are downloaded and cached on the device when tapped in the library. However, under certain conditions, such as when the device's free storage is running low or when a file hasn't been accessed for an extended period, iOS will automatically clear the cache to free up storage.

This behavior is consistent with other files stored in iCloud Drive and can be confirmed in 'Files' app. (Files in an undownloaded state display an icon with a cloud mark.)

While Booklover has a feature that allows users to manually request iOS to clear the cache of book files ('Clear Content Cache'), the app does not clear the cache on its own.

[Update: December 19, 2024]
On iOS 18, you can now retain cache on your device by selecting a file in the Files app, long-pressing it, and choosing "Keep Downloaded" from the displayed menu.

When manually selecting 'Clear Content Cache' from Booklover, the app requests iOS to clear the cache of that iCloud Drive file. However, it seems that the cache might not be cleared depending on the file's state. Furthermore, for smaller-sized files, even if the cache is cleared, the OS might automatically redownload them immediately.

In general, we recommend users not to be overly concerned with managing the cache of iCloud Drive files and to leave it to the OS.

First, check within the device's 'Files' app under the iCloud Drive's Booklover folder to see if the target book files for syncing exist. If the target files are not present in the 'Files' app, it indicates that the sync between the device and iCloud Drive hasn't taken place, and the target books will not be displayed in Booklover. In such cases, restarting the device may initiate the syncing process. (Note that it might take up to an hour for the sync to start in some cases.)

After confirming that the book files have been synced within the 'Files' app, try launching Booklover.

Yes, you can import files stored in cloud storage services such as Google Drive, OneDrive or Dropbox into Booklover.

To do so, tap the "Import" icon located at the left end of the toolbar at the bottom of the library. In the window that appears, select your desired service from "Locations" in the side menu and browse for your file.

Please ensure the following prerequisites are met before importing:

1. The app for the respective cloud storage service (e.g., the "Drive" app for Google Drive) is installed on your device.
2. You are logged in to the app.
3. The cloud storage service is enabled in the "Locations" section of the file app by editing settings.

To import book files stored in a cloud storage service using Booklover, you need to have the dedicated app provided by your cloud storage service installed on your device. (For example, if you have files in Dropbox, please install the Dropbox app from the App Store.) After the corresponding app is installed, tapping the 'Import' button on the left end of the toolbar at the bottom of the library will display the name of that service (app).

In most cases, restarting the device will initialize the OS's helper applications, resolving issues related to file imports. Please also make sure that your cloud storage service app is updated to the latest version.

E-books sold on platforms like Amazon typically have electronic restrictions (DRM) to protect copyrights, ensuring they can only be viewed on dedicated devices or apps. However, there are many publishers and indie book sales sites that sell e-books without applying DRM to the content. E-books purchased from these sites can be freely viewed on any app or device that supports their format. Of course, files you've created yourself, such as those scanned from physical books using a page scanner, documents saved in PDF format, or collections of your favorite images archived in ZIP or RAR formats, can also be viewed as DRM-free e-books in Booklover.

Currently, Booklover does not recognize 'nested' archive format files (e.g., a ZIP or RAR file within another ZIP or RAR file). If the contents of a ZIP or RAR file are solely another ZIP or RAR file, Booklover will treat the content as empty, resulting in an error when trying to open it as a book.

The current version does not support this.

Booklover does not support classification of books into folders. When you categorize a large number of books into folders, the operations needed to move from one book to another can become complex, making spontaneous book selection more challenging. Therefore, we recommend managing books through metadata (such as by genre, author name sorting, filtering by tag data) similar to how music files are managed on iTunes.

Manual rearrangement is currently not supported. As the number of books increases, manually sorting the library becomes progressively more challenging. Instead, we recommend sorting by phonetic order of author names, titles, etc.

The current version does not support this.