Most file leaks are not sophisticated attacks. They are ordinary mistakes: the wrong link permission, a forgotten metadata field, an unnecessary upload.
Files move constantly — between colleagues, clients, contractors, and devices. Each transfer is a moment where information can end up somewhere it should not. The good news is that the overwhelming majority of real-world exposures come from a short list of avoidable habits rather than from anything technically exotic.
Principle one: share the least you can
Data minimisation is the highest-leverage security practice available, and it requires no tools. Before sending anything, ask whether the recipient needs the entire document.
- Send the relevant pages rather than the whole report. Split PDF extracts a page range locally so you never distribute the sections nobody asked for.
- Crop screenshots to the region that matters. A full desktop capture can reveal other windows, tab titles, calendar entries, and notification content — use the Image Cropper to remove all of it.
- Strip columns and rows from spreadsheets that contain data outside the scope of the request.
- Prefer a summary to a raw dataset when the recipient only needs conclusions.
You cannot leak what you never sent.
Principle two: choose the channel deliberately
Different channels offer very different guarantees, and the convenient default is rarely the appropriate one for sensitive material.
Email attachments
Email is convenient and near-universal, but attachments are copied indefinitely across mail servers, backups, and recipients' devices. You cannot recall them, cannot expire them, and cannot see who forwarded them. Fine for routine documents; poor for anything confidential.
Cloud storage links
Links are better because access is revocable and auditable — but only if you configure them. The single most common cloud mistake is generating an "anyone with the link" URL for convenience and never revisiting it. Prefer named-recipient access, set expiry dates, and disable downloading when viewing suffices.
Managed transfer and client portals
For regulated data — health, financial, legal — use a system designed for it, with access logging, retention controls, and contractual protections. Convenience is not a defence in a compliance review.
Principle three: mind the metadata
Files carry information beyond their visible content, and people are frequently surprised by what travels with them.
- Photographs may embed GPS coordinates, capture time, device model, and serial numbers.
- Office documents retain author names, organisation details, editing time, and sometimes tracked changes and comments.
- PDFs preserve creator software, timestamps, and occasionally content hidden beneath redaction rectangles.
- Screenshots capture whatever else was on screen, including usernames and other applications.
Converting a file often drops much of this incidentally. Converting a phone photo with HEIC to JPG, for instance, produces a file that does not retain the original camera and location metadata. Re-encoding through the Image Converter has a similar effect. Neither is a substitute for a deliberate redaction process on genuinely sensitive documents, but both reduce casual leakage.
One warning about redaction: drawing a black rectangle over text in a PDF viewer does not remove the text. It draws a shape on top of it, and the text remains selectable underneath. Proper redaction removes the underlying content, and the only reliable verification is to search the final file for the words you intended to remove.
Principle four: prefer local processing
Every time you upload a file to an online tool to compress, convert, or merge it, you create a copy on infrastructure you do not control, governed by a privacy policy you probably have not read, with a retention period you cannot verify. For a holiday snapshot that is irrelevant. For a client contract, a payslip, or a medical letter it is a genuine exposure.
Browser-based tools eliminate the issue structurally. All Convert26 tools — including PDF Compressor, Merge PDF, and Image to Text (OCR) — process files locally in your browser using JavaScript. Nothing is transmitted, so there is nothing on a server to breach, subpoena, or forget to delete.
Principle five: control access over time
Sharing is not a single event. Access granted today persists until someone removes it, and the person who granted it usually forgets.
- Set expiry dates by default on shared links, even internal ones.
- Review shared items quarterly and revoke anything no longer needed.
- Remove access when projects end and when contractors or staff leave, as part of a written offboarding checklist.
- Use view-only permissions unless editing or downloading is genuinely required.
Principle six: verify the recipient
Autocomplete in email clients is responsible for a remarkable share of misdirected confidential documents. Two similar names, one keystroke, and a document reaches the wrong company. Before sending anything sensitive, read the recipient address in full rather than trusting the suggested name. For high-stakes transfers, confirm the address through a separate channel first.
A short pre-send checklist
- Is this the minimum content the recipient needs?
- Is the channel appropriate for this sensitivity level?
- Have I checked for metadata, comments, tracked changes, and hidden content?
- If I redacted anything, have I verified it is actually gone?
- Is the recipient address correct, read in full?
- Does this share have an expiry, and will I remember to review it?
- Did any part of this workflow upload the file somewhere unnecessary?
None of these steps is technically demanding. Applied consistently, they prevent almost every ordinary file-sharing incident — which is, in practice, almost every incident there is.