Guide

PDF24 vs Sejda vs iSharePDF: Which Tool Actually Protects Your Privacy?

iS By The iSharePDF team • Updated 2026-06-26 · 7 min read
Every time you drop a PDF into an online tool, you make a decision you might not have thought about: your file travels to a remote server, sits in memory or on disk, and only disappears after an automated retention timer runs. For a utility bill, that is probably fine. For a signed contract, a tax return or a patient report, the calculation changes. PDF24 and Sejda are two of the most widely used PDF platforms on the web, and both are genuinely capable tools. But both require an upload. iSharePDF takes a fundamentally different approach: every compression, merge, split or conversion runs entirely inside your browser, on your own hardware, with zero bytes transmitted to any external server. This guide gives you the real numbers so you can make the right call for each document.

How Each Tool Handles Your Files?

The most important question to ask about any PDF service is not how many tools it offers, but what it does with your file once you hit the process button. The answer divides tools into two categories: server-side and client-side.

Server-side tools like PDF24 online and Sejda upload your document to their infrastructure, run the operation on their hardware, then serve you the result. Your file exists on their servers for some period of time, from a few minutes to several hours, depending on their retention policy.

Client-side tools use WebAssembly and JavaScript PDF engines that run directly inside your browser tab. Your file is loaded into browser memory, processed by your own CPU, and the output is written straight to your Downloads folder. No bytes leave your network interface.

Why does this distinction matter in practice? Three concrete reasons. First, a security breach of the provider's infrastructure could expose your document during its retention window. Second, employees or automated systems may access files for abuse prevention or pipeline training even when terms of service say otherwise. Third, data residency rules in healthcare, law and financial services often prohibit uploading specific document types to third-party servers regardless of the provider's regulatory status.

Understanding this architectural split upfront makes the rest of this comparison straightforward to evaluate against your own requirements.

PDF24 Online: Generous Limits but Every File Uploads

PDF24 is operated by Geek Software GmbH, a German company. GDPR governs how your files are handled, and EU data protection standards apply. Their stated policy is that uploaded files are deleted from their servers after processing completes, generally within a few hours. For most everyday documents, that window is acceptable.

The online tool set is one of the most complete in the free tier: merge, split, compress, OCR, protect, sign, rotate and more than twenty additional operations. The free plan imposes no task rate limits and accepts files up to 100 MB per upload, making it one of the most generous free offerings in this space.

Where PDF24 earns genuine privacy credit is its desktop application for Windows. That app runs entirely offline, processing files locally without any network connection. If you handle sensitive documents regularly and work on Windows, the desktop app eliminates the upload concern entirely.

The limitation for privacy-focused workflows is the online version: you cannot use it without uploading. There is no hybrid mode that detects when a file is small enough to process in browser memory. Even compressing a 200 KB thumbnail goes through their servers.

PDF24 online also relies on standard HTTPS transport, which protects your file in transit but requires decryption on their server to perform the operation. That is unavoidable with any server-side architecture, but worth stating explicitly when you are evaluating vendors.

Sejda: EU Servers and a Two-Hour Deletion Window

Sejda is headquartered in the Netherlands and markets itself on EU-first infrastructure. Files are stored on servers within the European Union and deleted after two hours, which is among the shorter retention windows in this category. For vendor assessments that require documented EU data residency, that two-hour deletion policy can be a meaningful checkbox.

The interface is exceptionally clean. Drag your file in, select your parameters, download the result. The free tier is more restricted than PDF24: three tasks per hour, a maximum of 50 MB per file, and a 200-page cap. For occasional light use that is sufficient, but any batch workflow will hit the ceiling quickly.

Paid plans start at approximately $7.50 per month and raise limits to 200 MB per file with unlimited tasks. Sejda's OCR pipeline is particularly strong, handling scanned documents with dense columns or mixed-language layouts more accurately than many competitors at comparable price points.

Like PDF24, Sejda also offers a desktop application that processes files locally and eliminates the upload entirely. The desktop app is a separate download not surfaced in the main web workflow, so most casual users end up on the online version without realizing an offline alternative exists.

The core constraint remains: the browser-based Sejda experience requires your file to leave your device. EU servers and a two-hour deletion policy reduce exposure, but they do not eliminate it. They introduce a control you have to trust, rather than a design that makes the exposure impossible by default.

iSharePDF: Processing That Never Leaves Your Device

iSharePDF is built on a single architectural principle: your files never touch a server. The entire PDF engine runs in your browser using WebAssembly compiled from a native PDF library. When you compress a PDF, the file loads into browser memory, the compression algorithm runs on your CPU, and the output streams directly to your Downloads folder.

You can verify this yourself. Open your browser's network inspector (F12 in Chrome or Firefox, then the Network tab), drop a file into any tool, and run the operation. You will see zero outbound requests carrying file data. The only network activity is the initial page load of the WebAssembly module, which is cached locally after the first visit.

The 28 available tools cover the full range of everyday PDF work: merge multiple files, split a document by page range, convert to Word with the PDF to DOCX tool, run OCR on scanned pages, annotate, sign and password-protect with AES-256 encryption. The 100 MB file size limit reflects browser memory constraints rather than a server quota.

No account is required for any free tool. No email address, no tracking of document history, no file stored anywhere after you close the tab. For teams with strict data-handling policies or anyone working with personally identifiable information, that zero-footprint model is the correct default rather than an optional setting.

Speed and File Size: Real Numbers

Privacy architecture affects performance in ways that are not always obvious before you start timing. Server-side tools carry full round-trip latency: your file uploads, the remote server processes it, and the result downloads. Client-side tools depend on your local CPU and memory bandwidth with no network overhead.

Representative timings for compressing a 10 MB scanned PDF on a 100 Mbps connection with a mid-range laptop in 2026:

On a slower connection such as 20 Mbps upstream, a 10 MB file takes approximately 4 seconds just to reach the server before any processing begins. Local processing is unaffected by upload speed.

File size limits compared:

For workflows involving more than a few documents per session, Sejda's three-tasks-per-hour free cap becomes a significant blocker. Both PDF24 and iSharePDF let you process as many files as you need without throttling.

Password Protection and AES-256 Encryption

Adding a password to a PDF is one of the most common operations across all three tools. All three implement the PDF standard correctly using AES-256 encryption. The privacy-relevant difference is where the encryption key is generated and where it is applied.

With PDF24 and Sejda, you type your password into a form field, the password is sent to their server alongside your file, the server applies AES-256 to the document, and the protected file returns to you. Your password travels over HTTPS, so it is encrypted in transit. But the server decrypts the HTTPS channel and receives the password in plaintext in order to apply it to the PDF.

With iSharePDF's protect tool, the password you type stays on your device. The AES-256 encryption is applied by the WebAssembly PDF engine running inside your browser. No server ever receives the password or the unprotected document. The protection is applied before any data could leave the device, because no data leaves the device at all.

The inverse matters equally: unlocking a password-protected PDF with server-side tools hands the provider a decrypted copy of your document for the duration of the operation. Locally, the plaintext document exists only in browser memory and is cleared when the tab closes.

For documents subject to HIPAA, attorney-client privilege or financial data protection rules, client-side encryption is not simply a preference. It is often a compliance requirement that a server-side tool cannot satisfy regardless of the provider's certifications.

Choosing the Right Tool for Each Situation

None of these three tools is the right answer in every context. A practical framework:

Use PDF24 desktop if you are on Windows, process PDFs regularly, and want a fully offline experience at no cost. The desktop application is free, fast and covers virtually every operation. The online version is reasonable for non-sensitive documents when you do not want to install software locally.

Use Sejda paid if you need the strongest available OCR on complex scanned documents and your organization requires documented EU data residency for vendor procurement. The two-hour deletion policy and Netherlands infrastructure may satisfy compliance requirements that procurement teams need on paper. It is worth noting that client-side tools sometimes create friction in vendor assessments precisely because they have less documentation to offer, even though they are architecturally more private.

Use iSharePDF for any document you would not be comfortable emailing to a stranger. Signed contracts, tax returns, HR records, patient files, legal briefs: anything where even a brief window of server-side exposure creates risk. It is also the right choice when you are on a slow connection, when you need to process many files without hitting rate limits, or when you simply want to know exactly where your data is at every moment.

If you have used iLovePDF and are looking for a privacy-respecting replacement, the iSharePDF vs iLovePDF comparison covers that matchup in detail.

For most people handling a mix of document types, the sensible default is to use a local tool for anything sensitive and reserve server-side platforms for situations where offline processing genuinely cannot meet the need.

Frequently asked questions

Does PDF24 store your files after processing?

PDF24's stated policy is that files are automatically deleted from their servers after processing completes, typically within a few hours. The company operates under GDPR as a German entity. For a guarantee that no file ever reaches a server, use the offline PDF24 desktop application or a client-side tool that processes everything inside your browser without uploading.

Is Sejda safe to use for confidential documents?

Sejda stores files on EU servers in the Netherlands and deletes them after two hours, which is a short retention window for this category. Under GDPR that is a reasonable baseline. However, your file does leave your device and is decrypted on Sejda's infrastructure during processing. For documents covered by attorney-client privilege, HIPAA or similar regulations, a zero-upload tool is a more defensible choice.

What is the maximum file size for local browser-based PDF processing?

iSharePDF supports files up to 100 MB. This limit is set by browser memory constraints rather than a server quota and applies equally to all 28 tools. There is no hourly rate limit. If you need to work with a file larger than 100 MB, try using the split tool to break it into smaller segments first, then process each segment individually.

Which PDF tool is fastest for compressing large files?

Local tools are fastest because they eliminate round-trip network latency. A 10 MB PDF compresses in 2 to 5 seconds with client-side processing. PDF24 and Sejda both require a full server round trip, which adds 8 to 16 seconds on a 100 Mbps connection and considerably more on slower connections. On mobile broadband, the gap can reach 30 seconds or more for a large file.

Can I use these PDF tools without creating an account?

All three offer free access without mandatory sign-up. PDF24 online requires no account. Sejda allows free use without registration but limits you to three tasks per hour at 50 MB per file. Paid Sejda plans require an account. iSharePDF requires no account for any of its 28 free tools, stores no document history, and collects no email address. Pro features are available through a Stripe-powered upgrade with no persistent file storage.

Ready to try?

Your next PDF does not need to leave your device. Use the compress tool to shrink a large file in seconds, merge several documents into one, or lock a sensitive PDF with AES-256 password protection, all processed locally in your browser with no upload, no account and no file stored anywhere. Open the tool you need and your file stays yours from start to finish.

Open your PDFs in iSharePDF, no sign-up, 100% local by default.

Try iSharePDF free →