Interleave PDF Pages
Interleave pages from two PDFs by alternating pages (A1, B1, A2, B2…). Ideal for reassembling duplex scans.
Drop PDF A here or click to browse
Max 200MB
Drop PDF B here or click to browse
Max 200MB
Related tools
About Interleave PDF Pages
Interleave PDF Pages is an PDF tool that runs in your browser. Interleave pages from two PDFs by alternating pages (A1, B1, A2, B2…). Ideal for reassembling duplex scans. The page you are reading is the same workspace you will use to do the work: pick a file or paste your input, choose the options that matter to you, and the tool produces the result on your device.
Under the hood, Interleave PDF Pages uses the open-source pdf-lib JavaScript library to do the actual work. The tool accepts PDF as input, with a per-file ceiling of 200 MB so memory usage stays predictable on lower-end laptops and tablets. The engine ships as part of the page bundle, so once the page is loaded the tool keeps working even if your network connection drops.
Most people land on Interleave PDF Pages via a search at the moment they actually need the tool. That shapes the design: the page is a single screen with the input on one side, the controls in the middle, and the result on the other, so a first-time visitor can complete the job without reading documentation.
The architecture is local-first by design. Once the page is loaded, you can disconnect from the network and the tool still completes the job. The processing stack — the open-source pdf-lib JavaScript library and the small UI shell wrapping it — ships with the page itself, so the tool keeps working in offline conditions, on a captive-portal Wi-Fi, or behind a corporate proxy that limits what the tab can reach.
A practical note on limits: Interleave PDF Pages accepts inputs up to 200 MB per run, and the tool processes one input at a time to keep memory usage predictable. If you ever bump into the ceiling, the cause is the size of the input.
Workflow tip: Interleave PDF Pages pairs well with Reverse PDF Pages and Split Pages Horizontally. Other adjacent tools you may find useful are Extract Single PDF Page and N-Up PDF Tool. Because every tool is a separate page, you can mix and match the steps that match your job. Bookmark the ones you reach for the most.
Interleave PDF Pages sees the most use from students assembling reading packets and small-business owners sending invoices, but the design is intentionally generic enough that you do not need a specialist background to get a good result. The defaults aim at the most common case so a first-time user can get the right output without changing any settings.
When the job finishes, Interleave PDF Pages hands you the result as `{name}-interleaved.pdf`. Filenames are derived from your input where possible, so a quick batch of jobs leaves you with a tidy folder rather than a pile of generic "output (3)" files. Nothing is auto-saved on Favtoo's side because nothing was ever sent there.
The transformation in Interleave PDF Pages is deterministic — the same input plus the same options produces the same result every run. That predictability matters when the result has to match an upstream specification or be reproducible later.
Interleave PDF Pages is structured around the idea that a useful tool should be its own page. Open the page, do the work, close the tab — the page is the entire product. There is no onboarding flow because there is nothing to onboard into.
A few practical tips that experienced users of Interleave PDF Pages pick up over time. First, keep your default browser updated — the engine relies on standard web APIs and newer browser versions are noticeably faster than ones from a few years ago. Second, close other heavy tabs before processing a large input; the engine shares CPU and memory with whatever else is open. Third, if you re-run the same kind of job often, your last-used settings are remembered for the rest of the tab session, so subsequent runs are essentially one click.
Interleave PDF Pages fits the gap where opening a desktop app feels heavy and writing a script feels overkill. The page handles the common PDF document workflow task with sensible defaults so a single visit usually completes the job; for highly specialised work, a dedicated desktop application can offer more knobs to turn.
Common gotchas worth flagging: Interleave PDF Pages only accepts PDF, so if your file is in another format you will need to convert it first. The 200 MB ceiling is per-file, not per-session; you can run as many separate jobs as you like, but a single oversized input will be rejected on load.
That is the whole tool. Use Interleave PDF Pages for as long as it stays useful to you, and if it does, the catalog has many more tools built the same way. Each applies the same single-purpose discipline, so the way you used this page transfers to the next one you try.
How it works
- 1Open Interleave PDF Pages in your browser. The page loads quickly and the tool is ready to use the moment it becomes interactive.
- 2Select the PDF file you want to process — drag-and-drop and the file picker both work.
- 3Tweak the controls if the defaults are not quite right for your input. The options are kept short and labelled in plain language.
- 4Click to start the job. The engine (the open-source pdf-lib JavaScript library) processes the input in the page; you can watch the progress indicator until it completes.
- 5Save the output (`{name}-interleaved.pdf`) when it is ready.
- 6Re-run with different settings as often as you want. Each run produces a fresh output and the original file on disk is never modified.
Common use cases
- Compress a marketing deck so the email send-out finishes in seconds using Interleave PDF Pages.
- Lock a confidential document with a password before sharing externally.
- Send a polished, print-ready PDF to a client without watermarks.
- Strip blank or test pages from a scanned document.
- Split a 200-page exhibit bundle into one PDF per exhibit.
- Convert a bundle of forms into a single archival PDF.
- Rotate scanned pages that came in upside-down from the office scanner.
- Reorder pages of a multi-chapter scan into the correct reading order.
FAQ
How does it work?
Drop two PDFs. Pages are taken alternately: A1, B1, A2, B2, A3, B3… to create the merged output.
Unequal page counts?
Remaining pages from the longer PDF are appended at the end.
Duplex scanning?
Scan odd pages front-to-back (PDF A) and even pages back-to-front (PDF B), then interleave them.
Private?
Yes — everything runs in your browser. No file ever leaves your device.
Will Interleave PDF Pages ask me to pay to download the result?
Interleave PDF Pages is free to use. The processing runs in your browser, which keeps the per-user cost low enough that the tool can be offered openly. The download is the same file the engine produced — you can use it for as many runs as you need.
Is it safe to use Interleave PDF Pages on confidential files?
Your file is processed inside your browser by the open-source pdf-lib JavaScript library. The engine reads the file's bytes from your tab's memory, computes the result, and writes the result back into the tab. You can confirm what the page does by opening developer tools and watching the Network tab during a run — the requests you see are for the tool's static assets only.
What should I do if Interleave PDF Pages fails on my file?
Failures usually fall into one of three buckets: the input is in an unsupported format, the input is over the size cap, or the input is structurally malformed (a truncated download, a partial export, or a stream the engine does not recognise). The first two are easy to confirm — check that your file is one of PDF and that it is below 200 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
What permissions does Interleave PDF Pages need to function?
Interleave PDF Pages only needs the standard web platform — file picker access for the inputs you choose to load, and optionally clipboard access if you copy the result rather than downloading it. There is no microphone, camera, geolocation or background-permission request, because none of those are needed for the work the tool does.
How often is Interleave PDF Pages updated?
Interleave PDF Pages is updated whenever the underlying engine releases an improvement or a bug fix. Because the tool is delivered as a static page, every visit fetches the latest version automatically — there is no "version" to manage on your end. If a particular release ever changes default behaviour, the change is documented on Favtoo's changelog so you can confirm what shifted.
Does Interleave PDF Pages require a browser extension or plug-in?
No installation is needed. Interleave PDF Pages runs as a normal web page, with no browser extension, no native helper, and no separate desktop client to download. That is partly a privacy choice — extensions can request broad permissions, while a regular page is sandboxed by default — and partly a convenience one: you can use Interleave PDF Pages on any computer you have temporary access to without leaving anything installed on it.
How long does Interleave PDF Pages take to process a file?
Most jobs finish in seconds. Speed scales with input size and with how many CPU cycles your browser tab has available — the engine runs in your browser, so it shares resources with whatever else you have open. For inputs near the 200 MB ceiling, expect anywhere from a few seconds to roughly a minute on a typical laptop. Closing other heavy tabs noticeably speeds things up.