Signatures

Foxit PDF SDK for Android provides digital signature creation, verification, removal, and property management through the Core SDK. Digital signatures let recipients verify document origin and whether content was altered.

Built-in signing in UI Extensions

If you use the full reader (UI Extensions), the digital signature module (DigitalSignatureModule), handwriting signature module (SignatureModule), and signature panel (SignaturePanelModule) for viewing and verifying signatures are built in. No extra code is required.

Default supported signature types

The SDK includes default signature callbacks for these filter/subfilter pairs without a custom callback:

• Adobe.PPKLite + adbe.pkcs7.detached
• Adobe.PPKLite + adbe.pkcs7.sha1

Core Classes

Class	Description
Signature	Signature object; create, sign, verify, and manage properties. Created with PDFPage.addSignature(), retrieved with PDFDoc.getSignature()

Signature Key Constants

Set signature info with setKeyValue(int key, String value):

Constant	Value	Description
e_KeyNameSigner	0	Signer
e_KeyNameLocation	1	Location
e_KeyNameReason	2	Reason
e_KeyNameContactInfo	3	Contact info
e_KeyNameDN	4	Distinguished name
e_KeyNameText	5	Custom text

Appearance Flag Constants

Control appearance content with setAppearanceFlags(int flags):

Constant	Value	Description
e_APFlagLabel	0x0002	Show label
e_APFlagReason	0x0004	Show reason
e_APFlagSigningTime	0x0008	Show signing time
e_APFlagDN	0x0010	Show DN
e_APFlagLocation	0x0020	Show location
e_APFlagSigner	0x0040	Show signer
e_APFlagBitmap	0x0080	Show image
e_APFlagText	0x0100	Show custom text

Digest Algorithm Constants

Constant	Value	Description
e_DigestSHA1	0	SHA-1
e_DigestSHA256	1	SHA-256
e_DigestSHA384	2	SHA-384
e_DigestSHA512	3	SHA-512

Common Verification State Constants

After verification, use getState() with bitwise AND:

Constant	Description
e_StateUnsigned	Not signed
e_StateSigned	Signed
e_StateVerifyValid	Signature valid
e_StateVerifyInvalid	Signature invalid
e_StateVerifyChange	Document modified
e_StateVerifyNoChange	Document not modified
e_StateVerifyIssueValid	Issuer certificate valid
e_StateVerifyIssueExpire	Issuer certificate expired

Example: Sign and Verify

import com.foxit.sdk.pdf.PDFDoc;
import com.foxit.sdk.pdf.PDFPage;
import com.foxit.sdk.pdf.Signature;
import com.foxit.sdk.common.Progressive;
import com.foxit.sdk.common.fxcrt.RectF;

PDFDoc doc = new PDFDoc("path/to/Sample.pdf");
doc.load(null);
PDFPage page = doc.getPage(0);

// Add signature field
Signature signature = page.addSignature(new RectF(100, 600, 300, 700));

// Set appearance
signature.setAppearanceFlags(
    Signature.e_APFlagLabel | Signature.e_APFlagDN |
    Signature.e_APFlagReason | Signature.e_APFlagSigner |
    Signature.e_APFlagSigningTime | Signature.e_APFlagLocation
);

// Set signature info
signature.setKeyValue(Signature.e_KeyNameSigner, "张三");
signature.setKeyValue(Signature.e_KeyNameLocation, "北京");
signature.setKeyValue(Signature.e_KeyNameReason, "文档审批");
signature.setFilter("Adobe.PPKLite");
signature.setSubFilter("adbe.pkcs7.detached");

// Sign
Progressive progressive = signature.startSign(
    "/sdcard/cert.pfx", "123".getBytes(),
    Signature.e_DigestSHA256, "/sdcard/signed.pdf", null, null);
int state = Progressive.e_ToBeContinued;
while (state == Progressive.e_ToBeContinued) {
    state = progressive.resume();
}

// Verify all signatures in signed document
PDFDoc signedDoc = new PDFDoc("/sdcard/signed.pdf");
signedDoc.load(null);

int count = signedDoc.getSignatureCount();
for (int i = 0; i < count; i++) {
    Signature sig = signedDoc.getSignature(i);
    if (sig == null || sig.isEmpty()) continue;

    Progressive verifyProgress = sig.startVerify(null, null);
    int vState = Progressive.e_ToBeContinued;
    while (vState == Progressive.e_ToBeContinued) {
        vState = verifyProgress.resume();
    }

    int verifiedState = sig.getState();
    if ((verifiedState & Signature.e_StateVerifyValid) != 0) {
        // Signature valid
    }
}

Example: Custom Signing Time

setSignTime does not support arbitrary time formats directly. To set a custom time string, write it to the signature dictionary:

Signature signature = page.addSignature(rect);
signature.setAppearanceFlags(Signature.e_APFlagSigningTime | Signature.e_APFlagSigner);

PDFDictionary dict = signature.getSignatureDict();
dict.setAtString("M", "2025/01/14 10:30:00");

API Reference

See the API Reference for full Signature documentation.