Comparison

Bookends vs PDFOptim

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Bookends

Manage your research references and PDFs on your mobile device. Search online databases, import metadata, annotate PDFs, and organize your library. Offers basic functionality for free with optional one-time purchase and yearly subscription for advanced features like cloud sync and unlimited imports.

Highlights
  • Search online reference databases
  • Import metadata and PDFs
  • PDF annotation and markup
  • Barcode scanning for references
  • Cloud sync across devices
  • Share online libraries
  • Create multiple libraries
Features
Read full description

Bookends is the reference management app you've been looking for. The basic version offers: • Search online sites directly (arXiv, Google Books, Google Scholar, JSTOR, the Library of Congress, PubMed, PubMed Central, and Semantic Scholar) or use the built-in browser (EZProxy-compliant) to download reference metadata and PDFs (access privileges required). Searches can return a maximum of 20 references, and only 50 references can be stored in your personal database. • Use unique identifiers such as DOI, PMID, ISBN, or arXiv id to autofill references. • View the text of PDF annotations in a note stream, and create your own with our powerful PDF markup engine. • Barcode scanning, one per day. • And many more features designed to help you discover, organize, and use reference information. Standard, one-time purchase ($14.99): • No limit on searches or importing. Premium, yearly subscription ($14.99). Requires a Standard purchase. • Cloud sync with all your iOS devices and Bookends for Mac (separate purchase). • Share online libraries with colleagues. • Scan documents with Mellel Mobile*. • Create multiple libraries. • Unlimited barcode scanning. • Extract PDF annotations with deep links to annotations and text. • Convenient UI to add PDF notes to the library. • Automate your actions with Shortcuts. * iPad-only. Requires a Mellel Mobile Premium subscription. Subscription is for one year and has an auto-renew option. The subscription can be managed in iOS -> Settings > [your name] > Subscriptions. A subscription will renew if it isn't canceled at least 24 hours before the renewal date. If the subscription is not renewed, Premium will be disabled but Standard will continue to work. Terms of Service: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

About

PDFOptim

Easily compress and optimize PDF files on your iPhone and iPad. Reduce the size of large documents, saving storage space and transmission time. Offers both automatic and manual compression modes with advanced settings for image and vector graphics.

Highlights
  • Compress PDF documents
  • Optimize PDF files
  • Automatic compression mode
  • Manual compression mode
  • Adjust image resolution and quality
  • Optimize vector graphics
  • Support for password-protected PDFs
Features
Read full description

PDFOptim is a simple and intuitive way to compress, optimize and reduce PDF documents on iPhones and iPads. PDFOptim provides easy and effective ways to compress large image and graphics heavy PDF files. Inbuilt side-by-side preview to compare original and compressed PDF. * * * PDFOptim for Mac is also available on the Mac App Store. * * * Compressed PDF documents requires less disk space for storage and faster uploads and downloads saves transmission time and cost. PDFOptim rewrites the entire PDF documents using selected compression options as efficiently as possible without compromising the document's integrity. If your PDF documents are in another app (For Example Mail, DropBox or SkyDrive etc.) that uses the Open In… button, tap the button to open the PDF document in PDFOptim. You can also transfer PDF documents from your desktop computer via iTunes into PDFOptim application on your iPhone or iPad. KEY FEATURES: AUTO COMPRESSION MODE - PDFOptim analyze document’s contents and apply algorithm to generate a smallest possible PDF by maintaining the document’s visual quality. Choose one of the four predefined Auto compression methods and let the app do the hard work for you. No further user interaction required to provide technical compression options. MANUAL COMPRESSION MODE - Change compression options manually to generate optimum sized PDF of your need. You can choose compression options to set from Image Color Model, Image Resolution, JPEG Image Quality, Optimise vector graphics level and Advance option. - Image color model to choose from RGB, Gray and Mono. Selecting Monochrome color model option converts raster PDF contents into black and white which helps reduces PDF file size to greater extent. It is very helpful when compressing scanned books mainly containing text. - Image resolution ppi (pixels/inch) control to resize raster image contents. Downsampling at lower resolution decrease the file size dramatically. - Quality control. Set quality from lossless to least for resampling all raster images into PDF. It allows you to control compressed PDF size and viewing quality. -Advance options to remove PDF content properties like alternate images, page thumbnails, documents structure hierarchy and output intent. - Optimize vector graphics option removes superfluous information to reduce vector graphics heavy PDF. Increase in optimize vector from 'Level 1' to 'Level 5' reduces output PDF file size less to more respectively. This option is very useful when PDF content mainly consist of high precision vector graphics, Usually PDF drawing, note-taking and PDF markup apps creates large vector graphics heavy PDF files which can be compressed by this option efficiently. - Password protected PDF documents supported for compression using correct password. - Single or multiple compressed PDFs can be shared as single ZIP (*.zip) file. - Allows Compressed PDFs to Open In… another application, Mail, Message, Print, share PDFs to nearby iOS devices via AirDrop. - Use Copy to iTunes to save and share compressed PDFs on your desktop computer. PDF VIEWER: - Inbuilt PDF viewer with fully selectable and searchable text contents. Select and copy text to clipboard for further use. - Pinch out and Pinch in to ZoomIn and ZoomOut view and search feature to find a character, word and sentence. - Scroll through your document by thumbnail view or Go to page feature. Note: PDFOptim is standalone application running natively to compress PDF documents securely on your iOS device. You can refer User Manual for any assistance Or Contact Support. *The free version has limitation to export one compressed PDF per week. Get Premium to remove all restrictions and start exporting an unlimited number of compressed PDFs. Privacy Policy: http://rootrisetech.com/pdfoptim-privacy-policy Terms of Use(EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

Bookends4 screens
PDFOptim4 screens

Verdict

The call

The clearest difference is update cadence: Bookends at every 2 months against PDFOptim's every 5 months. PDFOptim's advantage is iOS requirement (15.6 vs 18.6). On price, rating, review sentiment and ratings volume there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Bookends sells 2 in-app purchases, starting at $14.99 per year and PDFOptim sells 3 in-app purchases, starting at $0.99 per month. Whichever you choose, the download price is not the number that matters.

ReceptionRating · Positive reviews · Number of ratings

On the App Store both sit at effectively the same score — 4.7 for Bookends against 4.7 for PDFOptim. Both are backed by a comparable volume of ratings — 398 and 292 respectively. Written reviews split almost evenly too, at 76% and 76% positive.

UpkeepUpdate frequency

Bookends ships an update every 2 months, PDFOptim every 5 months. The most recent releases landed on October 12, 2026 and October 8, 2026 respectively.

Scorecard2 real differences · 8 level
Bookends versus PDFOptim: the parameters behind the verdict, then further details
ParameterBookendsPDFOptim
PriceFreeFree
Rating4.7 (398 ratings)4.7 (292 ratings)
Positive reviews76.4% of reviews — better75.6% of reviews
Number of ratings398 — better292
Update frequencyEvery 2 months — betterEvery 5 months
AdsNoNo
In-app purchasesYesYes
MonetizationFree with in-app purchasesFree with in-app purchases
DevicesiPhone, iPadiPhone, iPad, iPod — better
Requires iOS18.615.6 — better
Further details — not scored
Size114 MB8 MB
Age rating4+4+
DeveloperSonny Software, LLCRootRise Technologies Pvt. Ltd.

Customer experience

Bookends

All ratings398 ratings
Positive92.2%
Neutral2.3%
Negative5.5%
Written reviews127 reviews
Positive76.4%
Neutral8.7%
Negative15.0%

PDFOptim

All ratings292 ratings
Positive93.5%
Neutral1.7%
Negative4.8%
Written reviews82 reviews
Positive75.6%
Neutral3.7%
Negative20.7%

User reviews

Bookends

From 398 App Store ratings

What we love

  • 🚀 Seamless sync across devices
  • 👍 Excellent PDF annotation tools
  • 🔒 Reliable and stable
  • 💡 Powerful reference management features
  • 👍 Responsive and helpful developer support

Room to improve

  • 🐛 Sync issues with iCloud and PDF files
  • 🔒 Subscription model for essential features
  • 👎 Outdated and clunky user interface
  • 🔒 Limited functionality on iOS without subscription

PDFOptim

From 292 App Store ratings

What we love

  • 👍 Excellent compression quality
  • 🚀 Efficient and fast performance
  • 👍 Simple and easy to use
  • 💰 Good value for money (one-time purchase)
  • 👍 No annoying subscriptions

Room to improve

  • 🐛 App not launching/freezing
  • 🐛 Doesn't work for certain file types (e.g., GoodNotes)
  • 🐛 Poor image quality/pixelation
  • 🐛 Compression not effective on all PDFs
  • 🐛 Confusing or illogical interface

Bugs and requests

Bookends

Reported bugs

3 issues
  • Incompatibility with iCloud Optimized Storage
  • Unreliable sync between desktop and mobile versions
  • Occasional data loss or corruption

Requested features

4 requests
  • Nested folders and tags for better organization
  • Automatic PDF metadata extraction
  • Improved search and filtering capabilities
  • Seamless integration with third-party services

PDFOptim

Reported bugs

11 issues
  • App not launching on iOS 18.0.1
  • App freezes during launch
  • App won't take purchases
  • Cannot optimize certain PDFs
  • Compression not effective on marked-up PDFs
Show 6 more
  • App no longer works after updates
  • File compressed to a slightly smaller size with no significant reduction
  • Graphics become unreadable or highly degraded
  • App crashes
  • Multitasking, drag and drop not working
  • Doesn't use full screen on new iPads

Requested features

6 requests
  • Support for iOS shortcuts
  • macOS version integration/cross-platform compatibility
  • Improved handling of specific file types like GoodNotes
  • Better optimization for handwritten notes within PDFs
  • Cloud storage for compressed documents (iCloud)
Show 1 more
  • Update for latest OS versions and multitasking features

In-app purchases

2 purchases

Bookends

Subscriptions1
  • Premium3 Months trial$14.991 Year
One-time1
  • Standard$14.99
3 purchases

PDFOptim

Subscriptions2
  • Premium : Monthly Access$0.991 Month
  • Premium : Yearly Access3 Days trial$2.991 Year
One-time1
  • Premium : Lifetime Access$4.99

Questions

Is Bookends free?
Bookends is free to download, with in-app purchases available.
Is PDFOptim free?
PDFOptim is free to download, with in-app purchases available.
Which has better reviews, Bookends or PDFOptim?
Bookends and PDFOptim are both rated 4.7 out of 5 on the App Store, from 398 and 292 ratings respectively.
Do Bookends or PDFOptim have ads?
Neither Bookends nor PDFOptim shows ads.
Which is updated more often, Bookends or PDFOptim?
Bookends ships an update every 2 months, and PDFOptim every 5 months. Most recently, Bookends was updated on October 12, 2026 and PDFOptim on October 8, 2026.

Other comparisons