Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteTo protect an archived webpage PDF with a SHA-256 reference, finish and save the PDF first, calculate its hash, then store the full hexadecimal digest in a separate checksum file or archive manifest that identifies the PDF. If the PDF changes afterward, calculate and record a new hash.
Calculate the hash of the final PDF
A SHA-256 hash is a fingerprint calculated from a file’s bytes. The command reads the PDF; it does not need a PDF-specific hashing feature. Run the command only after completing any edits, OCR, metadata changes, or signature operations that belong in the archived file.
macOS and other Unix-like systems
In Terminal, run shasum -a 256 followed by the PDF’s filename. For example:
shasum -a 256 "archived-page.pdf"On Linux systems with GNU coreutils, you can use:
sha256sum "archived-page.pdf"Each command prints the SHA-256 digest and the filename it read. Adobe documents these command forms for calculating a file fingerprint: Adobe Acrobat Sign Help.
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Windows PowerShell
In PowerShell, run:
Get-FileHash "archived-page.pdf" -Algorithm SHA256The output includes the algorithm, digest, and path. If the PDF is elsewhere, provide its full path, for example Get-FileHash "C:Archivearchived-page.pdf" -Algorithm SHA256.
Save a detached checksum record
Keep the digest outside the PDF, such as in archived-page.pdf.sha256.txt or an archive manifest. This keeps the file being checked separate from its reference value: adding the digest as text inside the PDF changes the PDF’s bytes and therefore changes its hash.
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- Finish the PDF and save it at its final location.
- Run the appropriate SHA-256 command against that exact file.
- Copy the complete hexadecimal digest into a sidecar text file or manifest.
- Identify the exact PDF filename and, where known, record the source URL and capture date as context.
- Keep the PDF and its checksum record together, and preserve the record as a trusted reference.
For example, the sidecar can state the filename, source URL, capture date, and full digest on clearly labeled lines. Do not rely on the digest alone to identify which capture or version it belongs to.
Verify the PDF later
Run the same SHA-256 command on the file you want to check and compare every hexadecimal character with the saved reference. A match means the checked file has the same digest as the reference. If the values differ, first confirm that you checked the same filename and version and used SHA-256; then investigate whether the PDF was changed or the reference belongs to another capture.
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What a matching hash can—and cannot—show
A matching digest supports a comparison that the current file has not changed relative to the file represented by a trusted reference digest. It does not, by itself, prove who created the PDF, when the webpage was captured, whether the page was complete, or whether the saved reference is trustworthy. Preserve source and capture context alongside the file. NARA defines web-record integrity in terms of completeness and lack of alteration, and identifies context and authenticity as broader recordkeeping concerns: NARA Guidance on Managing Web Records.
A PDF is one representation of a webpage, not necessarily a complete website record. It may omit links, interactive behavior, referenced resources, or related pages. For applicable federal web-record transfers, NARA guidance discusses retaining component parts, original links, functionality, data integrity, internally referenced URLs, and harvesting control information; it identifies WARC 1.0/1.1 and WACZ among preferred formats. Those formats are not mandatory for every personal or organizational archive. See NARA’s web-record guidance.
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Do not confuse a checksum with a PDF signature or PDF/A
Detached checksum and digital signature
A detached SHA-256 checksum is a digest stored outside the PDF for later comparison. A PDF digital signature is a signing operation associated with a signer identity and certificate. Adobe’s technical guide describes a signature digest calculated over PDF byte ranges while excluding the signature-value bytes; the digest is then signed and embedded. That is not the same as printing a standalone checksum into a document. See Adobe’s technical guide to digital signatures in PDF.
Adobe’s Acrobat security preferences describe SHA-256 as the default signing algorithm for Acrobat 9.1 and later, with a possible fallback to SHA-1 when a token cannot support SHA-256. This is a version-specific digital-signature setting, not a change to the detached file-hashing commands above: Adobe Acrobat security preferences.
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PDF/A and checksums serve different purposes
PDF/A is the ISO 19005 family of constrained PDF formats intended for long-term preservation of page-oriented documents. Its preservation aims include stable visual appearance through device independence, self-containment, and self-documentation. Choosing or validating PDF/A does not calculate or maintain a separate SHA-256 checksum. See the Library of Congress PDF/A format description.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshooting
- The command cannot find the file: Run it from the folder containing the PDF, or use the full path. Quote paths containing spaces, such as
"C:ArchiveArchived Page.pdf". - The digest differs from the saved reference: Confirm the algorithm is SHA-256 and that both checks were run on the same PDF version. If the file was edited, re-hash the final version and update the reference record.
- You added the hash to the PDF and the digest no longer matches: Any edit changes the bytes being hashed. Keep the digest in a sidecar or manifest instead, then calculate a fresh hash for the finished PDF.
- You need evidence of signer identity or a signed document: A detached checksum alone does not provide a signer identity or certificate-based signature. Use an appropriate PDF digital-signature workflow when that is the requirement.
- You need to preserve a website rather than a printable copy: A PDF may not retain the site’s interactive behavior and related resources. Consider a broader web-archive package appropriate to your organization’s requirements; NARA’s federal transfer guidance is one reference, not a universal mandate.
Or skip the browser setup
If you still need to create the webpage PDF, ScreenshotNeo can capture a URL in one request; you can then calculate the SHA-256 hash of the downloaded PDF using the commands above. ScreenshotNeo is a website screenshot API and MCP server from ScreenshotNeo. This PDF endpoint example captures a page directly as a PDF:
Quick Recap
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -d format=pdf -o archived-page.pdfSee the ScreenshotNeo API documentation for request options. Cookie banners, popups, and chat widgets are removed before the shot; bot checks, blank pages, and failed loads are never billed. Its MCP server lets AI agents take screenshots. The free plan includes 1,000 screenshots a month with no card, and paid plans start at $5 for 3,000. Sign up for ScreenshotNeo’s free plan.
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